Ledipasvir-Sofosbuvir (ledipasvir/sofosbuvir)

Ledipasvir/sofosbuvir is commercially available as fixed-combination pellets containing 33.75 mg of ledipasvir and 150 mg of sofosbuvir, fixed-combination pellets containing 45 mg of ledipasvir and 200 mg of sofosbuvir, fixed-combination tablets containing 45 mg of ledipasvir and 200 mg of sofosbuvir, and fixed-combination tablets containing 90 mg of ledipasvir and 400 mg of sofosbuvir.

Ledipasvir/sofosbuvir is administered orally once daily with or without food.

Ledipasvir/sofosbuvir is commercially available for oral administration as film-coated tablets and as pellets that should be swallowed whole or mixed with soft food and swallowed whole. The pellets can be used in pediatric patients who cannot swallow tablets.

Ledipasvir/sofosbuvir pellets taken with food: One or more spoonfuls of nonacidic soft food at or below room temperature (e.g., pudding, chocolate syrup, mashed potato, ice cream) should be added to a bowl. The entire contents of the appropriate number of single-dose packets of pellets (see Table 4) should be sprinkled onto the food and gently mixed with a spoon. No pellets should remain in the packet(s). The entire mixture containing the pellets should be ingested within 30 minutes after preparation; the pellets in the mixture should be swallowed whole without chewing to avoid a bitter aftertaste. Any unused portion of the mixture should be discarded and should not be stored or used later.

Ledipasvir/sofosbuvir pellets taken without food: The entire contents of a single-dose packet of pellets should be poured directly into the mouth and the pellets swallowed whole without chewing to avoid a bitter aftertaste. Water may be swallowed after the pellets, if needed. If 2 packets of pellets are indicated (see Table 4), the process should be repeated. No pellets should remain in the packet(s).

The following drug interactions are based on studies using the fixed combination of ledipasvir and sofosbuvir (ledipasvir/sofosbuvir), ledipasvir alone, or sofosbuvir alone. When ledipasvir/sofosbuvir is used, interactions associated with both drugs in the fixed combination should be considered.

Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

Ledipasvir/Rosuvastatin

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Rosuvastatin is a substrate for breast cancer resistance protein (BCRP).(1) Ledipasvir inhibits intestinal BCRP leading to increased systemic absorption of rosuvastatin.(2)

CLINICAL EFFECTS: High systemic concentrations of rosuvastatin increase the risk for statin-induced myopathy or rhabdomyolysis.

PREDISPOSING FACTORS: The risk for myopathy or rhabdomyolysis may be greater in patients 65 years and older, inadequately treated hypothyroidism, renal impairment, carnitine deficiency, malignant hyperthermia, or in patients with a history of myopathy or rhabdomyolysis. Patients with a SLCO1B1 polymorphism that leads to decreased function of the hepatic uptake transporter OATP1B1 may have increased statin concentrations and be predisposed to myopathy or rhabdomyolysis. Patients on rosuvastatin with ABCG2 polymorphisms leading to decreased or poor BCRP transporter function may have increased rosuvastatin concentrations and risk of myopathy.

PATIENT MANAGEMENT: The US manufacturer of rosuvastatin states that concurrent use of ledipasvir/sofosbuvir should be avoided.(1) Use an alternative statin during ledipasvir treatment for hepatitis C.

DISCUSSION: In a randomized cross-over interaction study, healthy subjects received ledipasvir, vedroprevir, tegobuvir (the latter two are investigational hepatitis C agents) for 9 days followed by one dose of either rosuvastatin or pravastatin on day ten, and then one dose of the other statin on day 14. After a 9-day washout, another identical treatment period was started except that the order of statin administration was reversed. This combination of 3 hepatitis C agents increased rosuvastatin area-under-curve (AUC) by 699%. The manufacturer attributes this large increase in exposure primarily to BCRP inhibition by ledipasvir.(3)

P-Glycoprotein (P-Gp) Inh/Colchicine (For Cardioprotection)

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibitors may affect the transport of colchicine, a P-gp substrate.(1,2)

CLINICAL EFFECTS: Concurrent use of a P-gp inhibitor may result in elevated levels of and toxicity from colchicine. Symptoms of colchicine toxicity include abdominal pain; nausea or vomiting; severe diarrhea; muscle weakness or pain; numbness or tingling in the fingers or toes; myelosuppression; feeling weak or tired; increased infections; and pale or gray color of the lips, tongue, or palms of hands.(1,2)

PREDISPOSING FACTORS: This interaction is expected to be more severe in patients with renal or hepatic impairment.(1,2)

PATIENT MANAGEMENT: The manufacturer of colchicine used for cardiovascular risk reduction states that concurrent use of colchicine with P-gp inhibitors is contraindicated.(1)

DISCUSSION: There are several reports of colchicine toxicity(3-5) and death(6,7) following the addition of clarithromycin to therapy. In a retrospective review of 116 patients who received clarithromycin and colchicine during the same hospitalization, 10.2% (9/88) of patients who received simultaneous therapy died, compared to 3.6% (1/28) of patients who received sequential therapy.(8) An FDA review of 117 colchicine-related deaths that were not attributable to overdose found that 60 deaths (51%) involved concurrent use of clarithromycin.(2) There is one case report of colchicine toxicity with concurrent erythromycin.(9) In a study in 20 subjects, pretreatment with diltiazem (240 mg daily for 7 days) increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of colchicine (0.6 mg) by 44.2% (range -46.6% to 318.3%) and by 93.4% (range -30.2% to 338.6%), respectively.(1) In a study in 24 subjects, pretreatment with verapamil (240 mg twice daily for 7 days) increased the Cmax and AUC of a single dose of colchicine (0.6 mg) by 40.1% (range -47.1% to 149.5%) and by 103.3% (range -9.8% to 217.2%), respectively.(1) Colchicine toxicity has been reported with concurrent use of CYP3A4 and P-gp inhibitors such as clarithromycin, cyclosporine, diltiazem, erythromycin, and verapamil.(1,2) P-gp inhibitors include abrocitinib, amiodarone, asciminib, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, cyclosporine, danicopan, daraxonrasib, daridorexant, deutivacaftor, diltiazem, diosmin, dronedarone, erythromycin, flibanserin, fluvoxamine, fostamatinib, glecaprevir/pibrentasvir, imlunestrant, ivacaftor, lapatinib, ledipasvir, mavorixafor, neratinib, osimertinib, pirtobrutinib, propafenone, quinidine, ranolazine, schisandra, selpercatinib, sotorasib, tepotinib, valbenazine, velpatasvir, vemurafenib, venetoclax, vepdegestrant, verapamil, vimseltinib, and voclosporin.(1,10,11)

P-Glycoprotein (P-Gp) Inhibitors/Doxorubicin

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibition may increase doxorubicin cellular concentration, as well as decrease biliary or renal elimination.(1)

CLINICAL EFFECTS: Increased cellular or systemic levels of doxorubicin may result in doxorubicin toxicity, including cardiomyopathy, myelosuppression, or hepatic impairment.(1)

PREDISPOSING FACTORS: The interaction magnitude may be greater in patients with impaired renal or hepatic function.

PATIENT MANAGEMENT: Avoid the concurrent use of P-gp inhibitors in patients undergoing therapy with doxorubicin.(1) Consider alternatives with no or minimal inhibition. If concurrent therapy is warranted, monitor the patient closely for signs and symptoms of doxorubicin toxicity. For patients on daraxonrasib, the manufacturer of daraxonrasib states that it should be taken at least 4 hours apart from P-gp substrates.(2)

DISCUSSION: Doxorubicin is a substrate of P-gp.(1) Clinical studies have identified and evaluated the concurrent use of doxorubicin and P-gp inhibitors as a target to overcome P-gp mediated multidrug resistance.(3,4) P-gp inhibitors linked to this monograph include: amiodarone, asciminib, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, cimetidine, cyclosporine, daclatasvir, danicopan, daraxonrasib, daridorexant, deutivacaftor, diltiazem, diosmin, dronedarone, eliglustat, erythromycin, flibanserin, fluvoxamine, fostamatinib, ginkgo, ginseng, glecaprevir/pibrentasvir, hydroquinidine, imlunestrant, istradefylline, ivacaftor, lapatinib, ledipasvir, mavorixafor, neratinib, osimertinib, paroxetine, pirtobrutinib, propafenone, quercetin, quinidine, quinine, ranolazine, sarecycline, schisandra, selpercatinib, simeprevir, sofosbuvir/velpatasvir/voxilaprevir, sotorasib, tepotinib, valbenazine, vemurafenib, vepdegestrant, verapamil, vimseltinib, and voclosporin.(5,6)

P-Glycoprotein (P-Gp) Inhibitors/Oral Lefamulin

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of P-glycoprotein (P-gp) may increase the absorption of lefamulin.(1) Oral lefamulin tablets may inhibit the metabolism of P-gp inhibitors that are also sensitive CYP3A4 substrates (i.e., asunaprevir, felodipine, ivacaftor, and neratinib).(1-3)

CLINICAL EFFECTS: The concurrent administration of lefamulin with an inhibitor of P-gp may result in elevated levels of lefamulin and signs of toxicity, such as QT prolongation. Coadministration of oral lefamulin with agents that are also sensitive CYP3A4 substrates (i.e., asunaprevir, felodipine, ivacaftor, and neratinib) may result in elevated levels and toxicities of the sensitive CYP3A4 substrate.

PREDISPOSING FACTORS: The risk of QT prolongation or torsade de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsade de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(4) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsade de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(4)

PATIENT MANAGEMENT: The US manufacturer of lefamulin states that oral lefamulin tablet coadministration with P-gp inhibitors should be avoided.(1) If concomitant therapy with a P-gp inhibitor is necessary, monitor patients closely for prolongation of the QT interval. Obtain serum calcium, magnesium, and potassium levels and monitor ECG at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting. Concomitant use of asunaprevir, felodipine, ivacaftor, or neratinib requires close monitoring for adverse effects of these drugs.(1) The manufacturer of venetoclax states that if concurrent use with a P-gp substrate cannot be avoided, take lefamulin at least 6 hours before venetoclax.(5)

DISCUSSION: Coadministration of ketoconazole (a strong CYP3A4 and P-gp inhibitor) with lefamulin tablets increased lefamulin area-under-the-curve (AUC) and maximum concentration (Cmax) by 165% and 58%.(1) In a study, oral lefamulin tablets administered concomitantly with and at 2 or 4 hours before oral midazolam (a CYP3A4 substrate) increased the area-under-curve (AUC) and maximum concentration (Cmax) of midazolam by 200% and 100%, respectively. No clinically significant effect on midazolam pharmacokinetics was observed when co-administered with lefamulin injection.(1) P-gp inhibitors include: asunaprevir, belumosudil, capmatinib, carvedilol, cimetidine, danicopan, daridorexant, diosmin, flibanserin, fluvoxamine, fostamatinib, ginseng, glecaprevir/pibrentasvir, hydroquinidine, ivacaftor, ledipasvir, neratinib, pirtobrutinib, propafenone, sofosbuvir/velpatasvir/voxilaprevir, tepotinib, valbenazine, vimseltinib, and voclosporin.(1-3)

P-Glycoprotein (P-Gp) Inhibitors/Topotecan

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of P-glycoprotein may increase the absorption of topotecan.(1)

CLINICAL EFFECTS: The concurrent administration of topotecan with an inhibitor of P-glycoprotein may result in elevated levels of topotecan and signs of toxicity. These signs may include but are not limited to anemia, diarrhea, and thrombocytopenia.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of topotecan states that the use of topotecan and P-glycoprotein inhibitors should be avoided. If concurrent use is warranted, carefully monitor patients for adverse effects.(1) For patients on daraxonrasib, the manufacturer of daraxonrasib states that it should be taken at least 4 hours apart from P-gp substrates.(2)

DISCUSSION: In clinical studies, the combined use of elacridar (100 mg to 1000 mg) increased the area-under-curve (AUC) of topotecan approximately 2.5-fold.(1) Oral cyclosporine (15 mg/kg) increased the AUC of topotecan lactone and total topotecan to 2-fold to 3-fold of the control group, respectively.(1) P-gp inhibitors linked to this monograph include: adagrasib, amiodarone, asciminib, asunaprevir, aumolertinib, azithromycin, belumosudil, bosutinib, carvedilol, cimetidine, clarithromycin, cobicistat, conivaptan, daraxonrasib, daridorexant, deutivacaftor, diltiazem, diosmin, dronedarone, erythromycin, flibanserin, ginseng, hydroquinidine, imlunestrant, isavuconazonium, itraconazole, ivacaftor, josamycin, ketoconazole, ledipasvir, lonafarnib, mavorixafor, neratinib, osimertinib, pibrentasvir/glecaprevir, posaconazole, propafenone, quinidine, ranolazine, selpercatinib, sotorasib, tepotinib, tucatinib, valbenazine, velpatasvir, vemurafenib, vepdegestrant, verapamil, vimseltinib, and voclosporin.(3,4)

Selected Hepatitis C Agents/P-Gp Inducers; Phenobarbital

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inducers of P-glycoprotein (P-gp) may decrease the absorption of ledipasvir,(1) sofosbuvir,(1-4) velpatasvir,(3,4) and voxilaprevir.(4)

CLINICAL EFFECTS: Concurrent or recent use of a P-gp inducer may result in decreased levels and effectiveness of ledipasvir,(1) sofosbuvir,(1-4) velpatasvir,(3,4) and voxilaprevir.(4)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturers of ledipasvir-sofosbuvir,(1) sofosbuvir,(2) sofosbuvir/velpatasvir,(3) and sofosbuvir-velpatasvir-voxilaprevir,(4) do not recommend coadministration with inducers of P-gp.

DISCUSSION: A study of 24 healthy subjects found that carbamazepine (300 mg twice daily) decreased the maximum concentration (Cmax) and exposure (AUC, area-under-curve) of sofosbuvir both by 48%.(3) In a study in 31 subjects, rifampin (600 mg daily) decreased the Cmax and AUC of ledipasvir by 35% and 59%, respectively.(1) In a study in 17 subjects, rifampin (600 mg daily) decreased the Cmax and AUC of sofosbuvir by 77% and 72%, respectively.(2-4) In a study in 12 subjects, rifampin (600 mg daily) decreased the Cmax and AUC of velpatasvir by 71% and 82%, respectively.(3-4) In a study in 24 subjects, rifampin (600 mg daily) decreased the Cmax and AUC of voxilaprevir by 9% and 73%, respectively.(4) Agents linked to this monograph include apalutamide, carbamazepine, fosphenytoin, lorlatinib, phenobarbital, phenytoin, primidone, rifampin, rifapentine, St. John's wort, and tipranavir.(1-6)

Selected Inhibitors Of P-Gp Or Bcrp/Pazopanib

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of P-glycoprotein (P-gp) or BCRP may increase the absorption of pazopanib.(1)

CLINICAL EFFECTS: The concurrent administration of pazopanib with an inhibitor of P-glycoprotein or BCRP may result in elevated levels of pazopanib and signs of toxicity.(1)

PREDISPOSING FACTORS: The risk of QT prolongation or torsade de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsade de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(2) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsade de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, and/or renal/hepatic dysfunction).(2)

PATIENT MANAGEMENT: The US manufacturer of pazopanib states concurrent use of P-gp inhibitors or BCRP inhibitors should be avoided.(1) Monitor patients for increased side effects from pazopanib. The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(5) If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting.

DISCUSSION: Pazopanib is a substrate of P-gp and BCRP. Inhibitors of these transporters are expected to increase pazopanib levels.(1) BCRP inhibitors linked to this monograph include: asciminib, belumosudil, clopidogrel, cyclosporine, curcumin, darolutamide, eltrombopag, enasidenib, febuxostat, fostemsavir, grazoprevir, lazertinib, leflunomide, leniolisib, momelotinib, oteseconazole, pirtobrutinib, regorafenib, resmetirom, ritonavir, rolapitant, roxadustat, tafamidis, teriflunomide, tolvaptan, turmeric, vadadustat, and zongertinib.(1,3-5) P-glycoprotein inhibitors linked to this monograph include: asunaprevir, belumosudil, capmatinib, carvedilol, cyclosporine, danicopan, daraxonrasib, daridorexant, diltiazem, flibanserin, fostamatinib, ginseng, glecaprevir/pibrentasvir, imlunestrant, isavuconazonium, ivacaftor, ledipasvir, neratinib, sofosbuvir/velpatasvir/voxilaprevir, tepotinib, tezacaftor, ticagrelor, valbenazine, verapamil, vimseltinib, and voclosporin.(3,4)

Sofosbuvir-Containing Hepatitis C Products/Rifabutin

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Rifabutin is an inducer of P-glycoprotein (P-gp) and may decrease the absorption of ledipasvir,(1-4) sofosbuvir,(1-12) velpatasvir,(5-12) and voxilaprevir.(9-12)

CLINICAL EFFECTS: Concurrent or recent use of rifabutin may result in decreased levels and effectiveness of ledipasvir,(1-4) sofosbuvir,(1-12) velpatasvir,(5-12) and voxilaprevir.(9-12)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The Australian and US manufacturers of ledipasvir-sofosbuvir,(1,4) velpatasvir-sofosbuvir,(5,8) and sofosbuvir-velpatasvir-voxilaprevir,(9,12) and the Canadian manufacturer of velpatasvir-sofosbuvir (6) do not recommend coadministration with rifabutin. The UK manufacturer of ledipasvir-sofosbuvir,(3) velpatasvir-sofosbuvir,(7) and sofosbuvir-velpatasvir-voxilaprevir,(11) and the Canadian manufacturer of sofosbuvir-velpatasvir-voxilaprevir (10) state that concurrent use with rifabutin is contraindicated.

DISCUSSION: In a phase I pharmacokinetic study with 20 healthy subjects, rifabutin (300 mg daily) decreased the maximum concentration (Cmax) and area-under-curve (AUC) of sofosbuvir by 36% and 24%, respectively.(8) The impact of rifabutin on ledipasvir, velpatasvir, and voxilaprevir has not been studied, but rifabutin is expected to lower plasma concentrations of each of these substances. Although a reduction in dose of sofosbuvir of less than 50% is not expected to reduce its efficacy, the potential impact of rifabutin on ledipasvir, velpatasvir, and voxilaprevir warrants caution with concomitant use.(13) In a study in 31 subjects, rifampin (600 mg daily, a strong P-gp inducer) decreased the maximum concentration (Cmax) and AUC of ledipasvir by 35% and 59%, respectively.(4) In a study in 17 subjects, rifampin (600 mg daily) decreased the Cmax and AUC of sofosbuvir by 77% and 72%, respectively.(4) In a study in 12 subjects, rifampin (600 mg daily) decreased the Cmax and AUC of velpatasvir by 71% and 82%, respectively.(8) In a study in 24 subjects, rifampin (600 mg daily) decreased the Cmax and AUC of voxilaprevir by 9% and 73%, respectively.(12)

Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

Ledipasvir/Simeprevir

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Ledipasvir may increase systemic absorption of simeprevir via inhibition of intestinal P-glycoprotein (P-gp).(1)

CLINICAL EFFECTS: Simeprevir systemic concentrations may be increased. Higher simeprevir exposure is associated with a higher incidence of rash which may be severe.(1,3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of ledipasvir states that concurrent administration with simeprevir is not recommended.(2) During the approval process, FDA reviewers evaluating ledipasvir interaction studies noted the approximate 2.4-fold increase in simeprevir exposure with this combination. Given the already large degree of interindividual variability in simeprevir pharmacokinetics and the higher risk for rash with increased exposure to simeprevir, they determined that safety concerns preclude concomitant use of this combination.

DISCUSSION: An interaction study in 22 healthy volunteers evaluated the combination of simeprevir (150 mg daily with food for 10 days) and ledipasvir (30 mg daily with food for 10 days; FDA reviewers believe the interaction magnitude would be similar at the approved ledipasvir dose of 90 mg). Simeprevir area-under-curve (AUC) and maximum concentration (Cmax) were increased 2.69-fold and 2.61-fold respectively. Given the already large degree of interindividual variability in simeprevir pharmacokinetics and the higher risk for rash with increased exposure to simeprevir, FDA reviewers determined that safety concerns preclude concomitant use of this combination.(1) In this interaction study, ledipasvir concentrations were also increased.(1,2) Based upon ledipasvir's safety profile, FDA determined the increased ledipasvir concentration does not present safety concerns.(1)

Ledipasvir; Velpatasvir/Proton Pump Inhibitors

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The aqueous solubility of ledipasvir and velpatasvir is pH dependent. Higher gastric pH leads to lower solubility which may reduce ledipasvir and velpatasvir absorption.(1-3)

CLINICAL EFFECTS: Coadministration of proton pump inhibitors (PPIs) may reduce the bioavailability of ledipasvir and velpatasvir, leading to decreased systemic levels and effectiveness.(1-3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Omeprazole 20 mg daily, or comparable doses of other PPIs, may be administered simultaneously with ledipasvir-sofosbuvir under fasting conditions.(1) Coadministration of proton pump inhibitors is not recommended with sofosbuvir-velpatasvir. When concomitant proton pump inhibitor use is necessary in patients receiving sofosbuvir-velpatasvir, velpatasvir-sofosbuvir should be administered with food and taken 4 hours before omeprazole 20 mg. Use with other proton pump inhibitors has not been studied.(2) Omeprazole 20 mg daily may be administered with sofosbuvir-velpatasvir-voxilaprevir. Use with other proton pump inhibitors has not been studied.(3) When clinically appropriate, consider use of H2 blockers or antacids.(1-3)

DISCUSSION: In an interaction study, omeprazole 20 mg given once daily simultaneously with ledipasvir-sofosbuvir, decreased ledipasvir exposure (AUC) by 4%. When omeprazole 20 mg once daily was given 2 hours prior to ledipasvir-sofosbuvir dose, ledipasvir exposure (AUC) decreased approximately 50%.(1) In an interaction study, omeprazole 20 mg given once daily simultaneously with sofosbuvir-velpatasvir decreased velpatasvir exposure (AUC) by 37%. When omeprazole 20 mg once daily was given 12 hours prior to sofosbuvir-velpatasvir dose, velpatasvir exposure (AUC) decreased 57%. When omeprazole 20 mg once daily was given 2 hours prior to sofosbuvir-velpatasvir dose, velpatasvir AUC decreased 48%. When omeprazole 20 mg once daily was given 4 hours after sofosbuvir-velpatasvir dose, velpatasvir AUC decreased 33%. When omeprazole 40 mg once daily was given 4 hours after sofosbuvir-velpatasvir dose, velpatasvir AUC decreased 56%.(2) In an interaction study, when omeprazole 20 mg once daily was given 2 hours prior to the sofosbuvir-velpatasvir-voxilaprevir dose, sofosbuvir AUC, velpatasvir AUC, and voxilaprevir AUC decreased 27%, 54%, and 20%, respectively. When omeprazole 20 mg once daily was given 4 hours after the sofosbuvir-velpatasvir-voxilaprevir dose, sofosbuvir AUC, velpatasvir AUC, and voxilaprevir AUC decreased 18%, 51%, and 5%, respectively %.(3) Proton pump inhibitors linked to this monograph are: dexlansoprazole, esomeprazole, lansoprazole, omeprazole, pantoprazole and rabeprazole.

Oatp1b1-3 Inhibitors/Brincidofovir

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: OATP1B1 and 1B3 inhibitors may increase the absorption and/or decrease the hepatic uptake of brincidofovir.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 or 1B3 inhibitors may result in elevated levels of and side effects from brincidofovir.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of brincidofovir states that alternative medications that are not OATP1B1 or 1B3 inhibitors should be considered. If concurrent use is necessary, instruct the patient to take the OATP1B1 or 1B3 inhibitor at least 3 hours after brincidofovir and increase monitoring for side effects, including transaminase and bilirubin elevations and GI side effects like diarrhea.(1)

DISCUSSION: In a clinical trial, single-dose oral cyclosporine (600 mg, an OATP1B1 and 1B3 inhibitor) increased the mean brincidofovir area-under-curve (AUC) and maximum concentration (Cmax) by 374% and 269%, respectively.(1) OATP1B1 and 1B3 inhibitors include: atazanavir, belumosudil, boceprevir, clarithromycin, cyclosporine, darunavir, eltrombopag, encorafenib, erythromycin, gemfibrozil, glecaprevir-pibrentasvir, ledipasvir, leflunomide, leniolisib, letermovir, lopinavir, ombitasvir-paritaprevir, paritaprevir, resmetirom, rifampin, ritonavir, roxadustat, saquinavir, simeprevir, sofosbuvir, telaprevir, teriflunomide, tipranavir, vadadustat, velpatasvir, and voclosporin.(1,2)

P-Glycoprotein (P-Gp) Inhibitors/Bilastine

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibition may increase the absorption of bilastine.(1,2)

CLINICAL EFFECTS: Concurrent use of P-gp inhibitors may result in elevated levels and toxicities from bilastine, including headache and somnolence.(1,2)

PREDISPOSING FACTORS: The interaction magnitude may be greater in patients with moderate to severe renal impairment.

PATIENT MANAGEMENT: The Canadian manufacturer of bilastine states that concomitant use of P-gp inhibitors with bilastine is not recommended. Coadministration should be avoided in patients with moderate or severe renal impairment.(1) The UK manufacturer of bilastine states that coadministration of bilastine and P-gp inhibitors should be avoided in patients with moderate to severe renal impairment.(2) The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(5)

DISCUSSION: In a study, ketoconazole and erythromycin both increased bilastine area-under-curve (AUC) and maximum concentration (Cmax) by 2-fold and 2- to 3-fold, respectively.(1) The UK manufacturer of bilastine states that these changes do not appear to affect the safety of bilastine.(2) P-gp inhibitors linked to this monograph include: amiodarone, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, cyclosporine, daclatasvir, danicopan, daraxonrasib, daridorexant, deutivacaftor, diltiazem, diosmin, dronedarone, eliglustat, erythromycin, flibanserin, fluvoxamine, fostamatinib, ginkgo, ginseng, glecaprevir/pibrentasvir, hydroquinidine, imlunestrant, istradefylline, ivacaftor, lapatinib, ledipasvir, mavorixafor, neratinib, osimertinib, paroxetine, pirtobrutinib, posaconazole, propafenone, quercetin, quinidine, quinine, ranolazine, sarecycline, schisandra, selpercatinib, simeprevir, sofosbuvir/velpatasvir/voxilaprevir, sotorasib, tepotinib, valbenazine, vemurafenib, vepdegestrant, verapamil, vimseltinib, and voclosporin.(4,5)

P-Glycoprotein (P-Gp) Inhibitors/Colchicine (For Gout & Fmf)

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibitors may affect the transport of colchicine, a P-gp substrate.(1,2)

CLINICAL EFFECTS: Concurrent use of a P-gp inhibitor may result in elevated levels of and toxicity from colchicine. Symptoms of colchicine toxicity include abdominal pain; nausea or vomiting; severe diarrhea; muscle weakness or pain; numbness or tingling in the fingers or toes; myelosuppression; feeling weak or tired; increased infections; and pale or gray color of the lips, tongue, or palms of hands.(1,2)

PREDISPOSING FACTORS: This interaction is expected to be more severe in patients with renal and/or hepatic impairment(1,2) and in patients who receive concurrent therapy.

PATIENT MANAGEMENT: The concurrent use of colchicine with P-gp inhibitors is contraindicated in patients with renal or hepatic impairment.(1-3) Avoid concurrent use in other patients, if possible.(3) In patients without renal or hepatic impairment who are currently taking or have taken a P-gp inhibitor in the previous 14 days, the dosage of colchicine should be reduced. For gout flares, the recommended dosage is 0.6 mg (1 tablet) for one dose. This dose should be repeated no earlier than in 3 days.(1,2) For gout prophylaxis, if the original dosage was 0.6 mg twice daily, use 0.3 mg daily. If the original dosage was 0.6 mg daily, use 0.3 mg every other day.(3-12) For Familial Mediterranean fever (FMF), the recommended maximum daily dose is 0.6 mg (may be given as 0.3 mg twice a day).(1,2) Patients should be instructed to immediately report any signs of colchicine toxicity, such as abdominal pain, nausea/significant diarrhea, vomiting; muscle weakness/pain; numbness/tingling in fingers/toes; unusual bleeding or bruising, infections, weakness/tiredness, or pale/gray color of the lips/tongue/palms of hands. The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(13)

DISCUSSION: There are several reports of colchicine toxicity(4-6) and death(7,8) following the addition of clarithromycin to therapy. In a retrospective review of 116 patients who received clarithromycin and colchicine during the same hospitalization, 10.2% (9/88) of patients who received simultaneous therapy died, compared to 3.6% (1/28) of patients who received sequential therapy.(9) An FDA review of 117 colchicine-related deaths that were not attributable to overdose found that 60 deaths (51%) involved concurrent use of clarithromycin.(2) There is one case report of colchicine toxicity with concurrent erythromycin.(10) In a study in 20 subjects, pretreatment with diltiazem (240 mg daily for 7 days) increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of colchicine (0.6 mg) by 44.2% (range -46.6% to 318.3%) and by 93.4% (range -30.2% to 338.6%), respectively.(1) In a study in 24 subjects, pretreatment with verapamil (240 mg twice daily for 7 days) increased the Cmax and AUC of a single dose of colchicine (0.6 mg) by 40.1% (range -47.1% to 149.5%) and by 103.3% (range -9.8% to 217.2%), respectively.(1) Colchicine toxicity has been reported with concurrent use of CYP3A4 and P-gp inhibitors such as clarithromycin, cyclosporine, diltiazem, erythromycin, and verapamil.(1,2) P-gp inhibitors include abrocitinib, amiodarone, asciminib, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, danicopan, daraxonrasib, daridorexant, deutivacaftor, diltiazem, diosmin, dronedarone, erythromycin, flibanserin, fluvoxamine, fostamatinib, glecaprevir/pibrentasvir, imlunestrant, ivacaftor, lapatinib, ledipasvir, mavorixafor, neratinib, osimertinib, pirtobrutinib, propafenone, quinidine, ranolazine, schisandra, selpercatinib, sotorasib, tepotinib, valbenazine, velpatasvir, vemurafenib, venetoclax, vepdegestrant, verapamil, vimseltinib, and voclosporin.(1,11,12)

P-Glycoprotein (P-Gp) Inhibitors/Pralsetinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibitors may inhibit cellular efflux of pralsetinib.(1)

CLINICAL EFFECTS: Concurrent administration of a P-gp inhibitor may result in elevated levels of and toxicity from pralsetinib, including hemorrhagic events, pneumonitis, hepatotoxicity, hypertension, and QTc prolongation, which may result in potentially life-threatening cardiac arrhythmias like torsades de pointes (TdP).(1-3)

PREDISPOSING FACTORS: The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(4) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(4)

PATIENT MANAGEMENT: Coadministration of pralsetinib with a P-gp inhibitor should be avoided.(1) If coadministration with a P-gp inhibitor cannot be avoided, use with caution and reduce the dose of pralsetinib as follows: -If the current dose is 400 mg once daily, decrease the dose to 300 mg daily. -If the current dose is 300 mg once daily, decrease the dose to 200 mg daily. -If the current dose is 200 mg once daily, decrease the dose to 100 mg daily. After the inhibitor is discontinued for three to five half-lives, resume the dose of pralsetinib at the dose taken prior to initiation of the inhibitor.(1) The manufacturer of venetoclax states that if concurrent use with a P-gp substrate cannot be avoided, take pralsetinib at least 6 hours before venetoclax.(5) The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(8) When concurrent therapy is warranted: consider obtaining serum calcium, magnesium, and potassium levels and monitoring EKG at baseline and regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting. If the QTc interval exceeds 500 ms, interrupt pralsetinib therapy until QTc is <470 ms. Resume pralsetinib at the same dose if risk factors that cause QT prolongation an are identified and corrected. If risk factors that cause QT prolongation are not identified, resume pralsetinib at a reduced dose. Permanently discontinue pralsetinib if the patient develops life-threatening arrhythmia.(3)

DISCUSSION: Coadministration of a single dose of cyclosporine 600 mg (a P-gp inhibitor) with a single pralsetinib 200 mg dose increased pralsetinib concentration maximum (Cmax) by 48% and area-under-curve (AUC) by 81%.(1) P-glycoprotein inhibitors linked to this monograph include: asunaprevir, belumosudil, carvedilol, cyclosporine, danicopan, daraxonrasib, daridorexant, deutivacaftor, diosmin, flibanserin, fostamatinib, ginseng, glecaprevir/pibrentasvir, ivacaftor, ledipasvir, neratinib, sofosbuvir/velpatasvir/voxilaprevir, tepotinib, valbenazine, venetoclax, vimseltinib, and voclosporin.(6,7)

Selected P-Glycoprotein (P-Gp) Inhibitors/Dabigatran

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Dabigatran etexilate is a substrate for the P-glycoprotein (P-gp) system. Inhibition of intestinal P-gp leads to increased absorption of dabigatran.(1-3)

CLINICAL EFFECTS: The concurrent use dabigatran with P-gp inhibitors may lead to elevated plasma levels of dabigatran, increasing the risk for bleeding.

PREDISPOSING FACTORS: Factors associated with an increased risk for bleeding include renal impairment, concomitant use of P-gp inhibitors, patient age >74 years, coexisting conditions (e.g. recent trauma) or use of drugs (e.g. NSAIDs) associated with bleeding risk, and patient weight < 50 kg.(1-4)

PATIENT MANAGEMENT: Assess renal function and evaluate patient for other pre-existing risk factors for bleeding prior to initiating concurrent therapy. The US manufacturer of dabigatran states that the concurrent use of dabigatran and P-gp inhibitors should be avoided in atrial fibrillation patients with severe renal impairment (CrCl less than 30 ml/min) and in patients with moderate renal impairment (CrCl less than 50 ml/min) being treated for or undergoing prophylaxis for deep vein thrombosis (DVT) or pulmonary embolism (PE). The interaction with P-gp inhibitors can be minimized by taking dabigatran several hours apart from the P-gp inhibitor dose.(1) The concomitant use of dabigatran with P-gp inhibitors has not been studied in pediatric patients but may increase exposure to dabigatran.(1) While the US manufacturer of dabigatran states that no dosage adjustment is necessary in other patients,(1) the Canadian manufacturer of dabigatran states that concomitant use of strong P-gp inhibitors (e.g., glecaprevir-pibrentasvir) is contraindicated. When dabigatran is used for the prevention of venous thromboembolism (VTE) after total hip or knee replacement concurrently with amiodarone, quinidine, or verapamil, the dose of dabigatran should be reduced from 110 mg twice daily to 150 mg once daily. For patients with CrCl less than 50 ml/min on verapamil, a further dabigatran dose reduction to 75 mg once daily should be considered. Verapamil should be given at least 2 hours after dabigatran to minimize the interaction.(2) The UK manufacturer of dabigatran also states the use of dabigatran with strong P-gp inhibitors (e.g., cyclosporine, glecaprevir-pibrentasvir or itraconazole) is contraindicated. Concurrent use of ritonavir is not recommended. When dabigatran is used in atrial fibrillation patients and for treatment of DVT and PE concurrently with verapamil, the UK manufacturer recommends reducing the dose of dabigatran from 150 mg twice daily to 110 mg twice daily, taken simultaneously with verapamil. When used for VTE prophylaxis after orthopedic surgery concurrently with amiodarone, quinidine, or verapamil, the dabigatran loading dose should be reduced from 110 mg to 75 mg, and the maintenance dose should be reduced from 220 mg daily to 150 mg daily, taken simultaneously with the P-gp inhibitor. For patients with CLcr 30-50 mL/min on concurrent verapamil, consider further lowering the dabigatran dose to 75 mg daily.(3) If concurrent therapy is warranted, monitor patients for signs of blood loss, including decreased hemoglobin and/or hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. Consider regular monitoring of hemoglobin, platelet levels, and/or activated partial thromboplastin time (aPTT) or ecarin clotting time (ECT). When applicable, perform agent-specific laboratory test (e.g. INR, aPTT) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(10)

DISCUSSION: When dabigatran was co-administered with amiodarone, the extent and rate of absorption of amiodarone and its active metabolite DEA were essentially unchanged. The dabigatran area-under-curve (AUC) and maximum concentration (Cmax) were increased by about 60% and 50%, respectively;(1,2) however, dabigatran clearance was increased by 65%.(1) Pretreatment with quinidine (200 mg every 2 hours to a total dose of 1000 mg) increased the AUC and Cmax of dabigatran by 53% and 56%, respectively.(1,2) Chronic administration of immediate release verapamil one hour prior to dabigatran dose increased dabigatran AUC by 154%.(4) Administration of dabigatran two hours before verapamil results in a negligible increase in dabigatran AUC.(1) Administration of sofosbuvir-velpatasvir-voxilaprevir (400/100/200 mg daily) increased the Cmax and AUC of a single dose of dabigatran (75 mg) by 2.87-fold and 2.61-fold, respectively.(5) Simultaneous administration of glecaprevir-pibrentasvir (300/120 mg daily) with a single dose of dabigatran (150 mg) increased the Cmax and AUC by 2.05-fold and 2.38-fold, respectively.(6) A retrospective comparative effectiveness cohort study including data from 9,886 individuals evaluated adverse bleeding rates with standard doses of oral anticoagulants with concurrent verapamil or diltiazem in patients with nonvalvular atrial fibrillation and normal kidney function. The study compared rates of bleeding following co-administration of either dabigatran, rivaroxaban, or apixaban with verapamil or diltiazem, compared to co-administration with amlodipine or metoprolol. Results of the study found that concomitant dabigatran use with verapamil or diltiazem was associated with increased overall bleeding (hazard ratio (HR) 1.52; 95% confidence interval (CI), 1.05-2.20, p<0.05) and increased overall GI bleeding (HR 2.16; 95% CI, 1.30-3.60, p<0.05) when compared to amlodipine. When compared to metoprolol, concomitant dabigatran use with verapamil or diltiazem was also associated with increased overall bleeding (HR, 1.43; 95% CI, 1.02-2.00, p<0.05) and increased overall GI bleeding (HR, 2.32; 95% CI, 1.42-3.79, p<0.05). No association was found between increased bleeding of any kind and concurrent use of rivaroxaban or apixaban with verapamil or diltiazem.(7) A summary of pharmacokinetic interactions with dabigatran and amiodarone or verapamil concluded that concurrent use is considered safe if CrCl is greater than 50 ml/min but should be avoided if CrCl is less than 50 ml/min in VTE and less than 30 ml/min for NVAF. Concurrent use with diltiazem was considered safe.(9) P-gp inhibitors include amiodarone, asunaprevir, aumolertinib, belumosudil, capmatinib, carvedilol, cimetidine, conivaptan, cyclosporine, daclatasvir, danicopan, daraxonrasib, daridorexant, diosmin, erythromycin, flibanserin, fostamatinib, ginseng, glecaprevir, imlunestrant, indinavir, itraconazole, ivacaftor, josamycin, lapatinib, ledipasvir, lonafarnib, mavorixafor, neratinib, osimertinib, pibrentasvir, posaconazole, propafenone, quinidine, ranolazine, ritonavir, selpercatinib, sotorasib, telaprevir, telithromycin, tepotinib, tezacaftor, tucatinib, valbenazine, velpatasvir, vemurafenib, vepdegestrant, verapamil, vimseltinib, voclosporin, and voxilaprevir.(1-9)

Sofosbuvir + Selected Direct Acting Antivirals/Amiodarone

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The exact mechanism is unknown.(1-7)

CLINICAL EFFECTS: Concurrent or recent use of amiodarone with sofosbuvir plus another direct acting antiviral may result in symptomatic bradycardia, which can be life-threatening, and cardiac arrest.(1-7)

PREDISPOSING FACTORS: Patients who are also receiving a beta-blocker or who have underlying cardiac comorbidities and/or advanced liver disease may be at a higher risk of developing symptomatic bradycardia.(1-7)

PATIENT MANAGEMENT: Concurrent use is potentially life-threatening. The FDA advises that sofosbuvir/ledipasvir or sofosbuvir combined with another direct acting antiviral should not be combined with amiodarone(1) and the manufacturer states concurrent therapy should only be used when other alternative antiarrhythmic treatments are not tolerated or contraindicated.(2-7) The AASLD/IDSA hepatitis C guidelines state patients being treated with amiodarone should not receive sofosbuvir-based regimens due to risk of life-threatening arrhythmias. Due to the long half-life of amiodarone, the guidelines advise that persons should be off amiodarone for at least 6 months before initiating sofosbuvir. If alternatives are deemed not to be clinically appropriate and the decision is made to start sofosbuvir in this setting, continued vigilance for bradycardia should be exercised.(8) If alternative treatment options are unavailable, or if sofosbuvir is initiated in a patient in whom amiodarone was discontinued in the previous three months, counsel patients about the risk of serious symptomatic bradycardia. Patients should undergo cardiac monitoring in an in-patient setting for the first 48 hours of coadministration and should then self-monitor their heart rate (or be monitored in a doctor's office) on a daily basis for at least the first two-weeks of treatment.(1-7) Instruct patients receiving concurrent therapy (and patients in whom amiodarone was recently discontinued) to seek medical attention immediately if they develop signs of symptomatic bradycardia, which may include: near-fainting or fainting, dizziness or lightheadedness, malaise, weakness, excessive tiredness, shortness of breath, chest pains, and/or confusion or memory problems.(1-7)

DISCUSSION: Nine cases of symptomatic bradycardia have been reported with sofosbuvir in combination with ledipasvir (n=3), simeprevir (n=1), or daclatasvir (n=5; marketed internationally, investigational agent in US). Seven patients were also receiving a beta-blocker. Six cases occurred within the first 24 hours of concurrent therapy, while the other cases occurred within 2-12 days of initiation of concurrent therapy. One case involved a fatal cardiac arrest and 3 required pacemaker insertion. In 3 cases, symptomatic bradycardia recurred following rechallenge with sofosbuvir. In one case, amiodarone was discontinued and sofosbuvir was re-initiated 8 weeks later with no reoccurrence of bradycardia.(1,2)

Moderate Interaction: Assess the risk to the patient and take action as needed.

Cyp2b6 And Selected Cyp3a4 Inducers/Levomethadone; Methadone

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: CYP2B6 inducers, phenytoin, and St. John's wort may increase the metabolism of levomethadone and methadone.(1-7)

CLINICAL EFFECTS: Concurrent use of CYP2B6 inducers, phenytoin, or St. John's wort may result in decreased levels of levomethadone and methadone, which may result in decreased effectiveness and may precipitate withdrawal symptoms.(1-7)

PREDISPOSING FACTORS: Induction effects may be more likely with regular use of the inducer for longer than 1-2 weeks.

PATIENT MANAGEMENT: Patients maintained on levomethadone or methadone may require dosage adjustments if a CYP2B6 inducer, phenytoin, or St. John's wort is initiated or discontinued. The effects of the interaction may last for several weeks after the discontinuation of the inducer.

DISCUSSION: In a study, efavirenz (600 mg daily) given for 3 weeks in patients on levomethadone led to a decrease in maximum concentration (Cmax) and area-under-curve (AUC) of levomethadone of 48 % and 57 %, respectively.(2) There are three case reports of patients in methadone maintenance programs who experienced withdrawal symptoms following the initiation of rifampin for tuberculosis therapy.(7,8) In one of these patients, the methadone clearance was measured at 8.97 ml/min/kg during concurrent administration of rifampin, compared with 2.11 ml/min/kg during methadone alone.(7) Other reports have documented that methadone-treated patients who received concurrent antituberculosis therapy which included rifampin experienced withdrawal symptoms while methadone-treated patients who received antituberculosis therapy which did not include rifampin did not.(9-12) Subsequently, it was determined that methadone plasma concentrations were decreased 33% to 68% in patients receiving concurrent rifampin compared with patients on non-rifampin regimens.(9,11-12) In a study in five patients maintained on methadone, the addition of phenytoin to their regimens resulted in moderately severe withdrawal symptoms and a decrease in the area-under-curve (AUC) for methadone. Methadone plasma concentrations returned to baseline levels two to three days after the discontinuation of phenytoin.(6) In a study in four patients in a methadone maintenance program, the addition of St. John's wort (900 mg daily) decreased methadone levels by 47% (range: 19%-60%). Two patients reported withdrawal symptoms.(7) CYP2B6 inducers linked to this monograph include: carbamazepine, dipyrone, isavuconazonium, ledipasvir/sofosbuvir, phenobarbital, primidone, rifampin, and sparsentan. Fosphenytoin, phenytoin and St. John's wort are also linked.

Cyp3a4; Cyp2c8; P-Glycoprotein (P-Gp) Inhibitors/Loperamide

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Inhibitors of CYP3A4, CYP2C8, and/or P-gp may increase loperamide systemic absorption and facilitate entry into central nervous system (CNS).(1)

CLINICAL EFFECTS: Concurrent use of inhibitors of CYP3A4, CYP2C8, and/or P-gp may increase levels of loperamide, resulting in respiratory depression.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Use loperamide with caution in patients receiving inhibitors of CYP3A4, CYP2C8, and/or P-gp. Consider lower doses of loperamide in these patients and monitor for adverse effects. The manufacturer of lonafarnib recommends starting loperamide at a dose of 1 mg and slowly increasing the dose as needed.(2)

DISCUSSION: In a randomized, cross-over study in 12 healthy subjects, itraconazole (100 mg twice daily for 5 days - first dose 200 mg), gemfibrozil (600 mg twice daily), and the combination of itraconazole and gemfibrozil (same dosages) increased the area-under-curve (AUC) of single doses of loperamide (4 mg) by 2.9-fold, 1.6-fold, and 4.2-fold, respectively.(3) In a study of healthy subjects, lonafarnib (100 mg twice daily for 5 days) increased the AUC and maximum concentration (Cmax) of single dose loperamide (2 mg) by 299% and 214%, respectively.(3) In a study in 18 healthy males, quinidine increased the AUC of a single dose of loperamide by 2.2-fold and markedly decreased pupil size.(4) In a study in 8 healthy subjects, subjects experienced respiratory depression when a single dose of loperamide (16 mg) was administered with a single dose of quinidine (600 mg) but not when loperamide was administered alone.(6) Loperamide plasma levels increased 2-fold to 3-fold.(5) Coadministration of trofinetide 12,000 mg twice daily with 4 mg of loperamide increased the AUC of loperamide by 1.73-fold and the Cmax by 1.95-fold. Administration of trofinetide 2 hours prior to loperamide increased the AUC of loperamide by 1.22-fold and the Cmax by 1.44-fold.(7)

Ledipasvir/Elvitegravir-Cobicistat-Tenofovir Disoproxil

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Tenofovir is a substrate of the P-glycoprotein (P-gp) and BCRP transporters.(1) Ledipasvir inhibits P-gp and BCRP.(2)

CLINICAL EFFECTS: Coadministration of ledipasvir with tenofovir disoproxil (TDF) (given as the fixed-dose combination of elvitegravir-cobicistat-TDF-emtricitabine) may increase the levels and toxicity of tenofovir, including new onset or worsening renal impairment, acute renal failure and Fanconi syndrome.(2,3)

PREDISPOSING FACTORS: Patients with baseline impaired renal function or who are receiving concomitant nephrotoxic agents may have an increased risk of renal-related adverse events.(3)

PATIENT MANAGEMENT: The manufacturers of ledipasvir-sofosbuvir and elvitegravir-cobicistat-TDF-emtricitabine state that coadministration of these two combinations is not recommended.(2,3)

DISCUSSION: Concurrent use of ledipasvir-sofosbuvir and elvitegravir-cobicistat-TDF-emtricitabine has not been studied. Since the safety of this combination is unknown, coadministration is not recommended.(2,3) Ledipasvir-sofosbuvir has been studied in combination with elvitegravir-cobicistat-tenofovir alafenamide-emtricitabine. In healthy subjects, the area-under-curve (AUC) of tenofovir decreased by 14% when coadministered with ledipasvir-sofosbuvir.(4) In clinical trials, ledipasvir-sofosbuvir increased the AUC of TDF (given in combination with atazanavir-ritonavir or darunavir-ritonavir) by 1.35- to 1.5-fold. When TDF was given in combination with efavirenz, rilpivirine, or dolutegravir, concurrent use of ledipasvir-sofosbuvir increased the AUC of tenofovir by about 2-fold.(1)

Ledipasvir; Velpatasvir/Antacids; H2 Antagonists

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: The aqueous solubility of ledipasvir and velpatasvir is pH dependent. Higher gastric pH leads to lower solubility which may reduce ledipasvir and velpatasvir's absorption.(1-3)

CLINICAL EFFECTS: Administration of antacids and H2 antagonists may reduce the bioavailability of ledipasvir and velpatasvir, leading to decreased systemic levels and effectiveness.(1-3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: In order to assure systemic absorption and maximal effectiveness from use of this Hepatitis C treatment, counsel patient to separate products containing ledipasvir or velpatasvir from antacid administration by 4 hours.(1-3) H2 antagonists may be administered simultaneously or 12 hours apart from products containing ledipasvir or velpatasvir at a dose that does not exceed doses comparable to famotidine 40 mg twice daily (or a total daily dose comparable to famotidine 80 mg).(1-3) Some vitamin preparations may contain sufficient quantities of calcium and/or magnesium salts with antacid properties to interact as well.

DISCUSSION: In an interaction study, famotidine 40 mg, given with or 12 hours after a ledipasvir-sofosbuvir dose did not have significant effects on ledipasvir-sofosbuvir exposure.(1) In an interaction study, famotidine 40 mg, given with or 12 hours prior to a velpatasvir-sofosbuvir dose did not have a significant effect on velpatasvir-sofosbuvir exposure.(2) In an interaction study, famotidine (dosage not stated) did not have a significant effect on the pharmacokinetic of sofosbuvir, velpatasvir, or voxilaprevir.(3)

Oatp1b1-3 Inhibitors/Atogepant

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Atogepant is a substrate of OATP1B1 and 1B3. Inhibitors of these transporters may increase the GI absorption and/or decrease the hepatic uptake of atogepant.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 or 1B3 inhibitors may result in elevated levels of and side effects from atogepant, including nausea, constipation and fatigue.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of atogepant states that, when used concurrently with an OATP inhibitor for prevention of episodic migraine, the atogepant dose should be limited to 10 mg or 30 mg once daily. When used concurrently with an OATP inhibitor for prevention of chronic migraines, the atogepant dose should be limited to 30 mg once daily.(1)

DISCUSSION: In a clinical trial of healthy subjects, single-dose rifampin, an OATP inhibitor, increased the atogepant area-under-curve (AUC) and maximum concentration (Cmax) by 2.85-fold and 2.23-fold, respectively.(1) OATP1B1 and 1B3 inhibitors include: atazanavir, belumosudil, cyclosporine, darunavir, eltrombopag, erythromycin, gemfibrozil, glecaprevir-pibrentasvir, ledipasvir, leflunomide, leniolisib, letermovir, paritaprevir, resmetirom, ritonavir, roxadustat, simeprevir, sofosbuvir, teriflunomide, vadadustat, velpatasvir, and voclosporin.(1,2)

Oatp1b1-3 Inhibitors/Momelotinib

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: OATP1B1 and 1B3 inhibitors may decrease the hepatic uptake of momelotinib.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 and 1B3 inhibitors may result in elevated levels of and side effects from momelotinib, including myelosuppression and hepatotoxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent use of momelotinib with OATP1B1 and 1B3 inhibitors should be approached with caution. Monitor patients closely for adverse reactions and consider dose modifications per momelotinib prescribing recommendations.(1)

DISCUSSION: Concurrent administration of a single dose rifampin, an OATP1B1/1B3 inhibitor, increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of momelotinib by 40% and 57%, respectively. The M21 metabolite Cmax increased 6% and AUC increased 12%.(1) OATP1B1 inhibitors include: atazanavir, belumosudil, boceprevir, cobicistat, cyclosporine, darolutamide, darunavir, eltrombopag, enasidenib, encorafenib, erythromycin, fostemsavir, gemfibrozil, glecaprevir-pibrentasvir, ledipasvir, letermovir, lopinavir, nirmatrelvir, paritaprevir, resmetirom, rifampin, roxadustat, saquinavir, simeprevir, telaprevir, tipranavir, vadadustat, velpatasvir, and voclosporin.(1,2)

P-Glycoprotein (P-Gp) Inhibitors/Afatinib

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Inhibitors of P-glycoprotein (P-gp) may increase the absorption of afatinib.(1)

CLINICAL EFFECTS: The concurrent administration of afatinib with an inhibitor of P-glycoprotein may result in elevated levels of afatinib and signs of toxicity. These signs may include but are not limited to worsening diarrhea, stomatitis, skin rash/exfoliation/bullae or paronychia.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of afatinib states the afatinib dose should be reduced by 10 mg if the addition of a P-glycoprotein inhibitor is not tolerated.(1) If afatinib dose was reduced due to addition of a P-gp inhibitor, resume the previous dose after the P-gp inhibitor is discontinued.(1) The manufacturer of vimseltinib states concurrent use with P-gp substrates should be avoided. If concurrent use cannot be avoided, take vimseltinib at least 4 hours prior to afatinib.(2) The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(4)

DISCUSSION: A drug interaction study evaluated the effects of ritonavir 200 mg twice daily on afatinib exposure. Administration of ritonavir 1 hour before afatinib administration increased systemic exposure by 48%. Afatinib exposure was not changed when ritonavir was administered simultaneously with or 6 hours after afatinib dose.(1) P-glycoprotein inhibitors linked to this monograph are: amiodarone, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, clarithromycin, cobicistat, cyclosporine, danicopan, daraxonrasib, daridorexant, deutivacaftor, diosmin, dronedarone, erythromycin, flibanserin, fostamatinib, ginseng, glecaprevir/pibrentasvir, hydroquinidine, imlunestrant, isavuconazonium, itraconazole, ivacaftor, josamycin, ketoconazole, lapatinib, ledipasvir, lonafarnib, mavorixafor, neratinib, osimertinib, posaconazole, propafenone, quinidine, ranolazine, ritonavir, saquinavir, selpercatinib, sofosbuvir/velpatasvir/voxilaprevir, sotorasib, telaprevir, tepotinib, tucatinib, valbenazine, vemurafenib, vepdegestrant, verapamil, vimseltinib and voclosporin.(1-3)

Select P-Gp Inhibitors/Edoxaban (<= 30 Mg)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Edoxaban is a substrate for P-glycoprotein (P-gp). Inhibitors of P-gp may increase intestinal absorption and decrease renal tubular elimination of edoxaban.(1,2)

CLINICAL EFFECTS: Concurrent use with selected P-gp inhibitors may result in higher systemic concentrations of edoxaban which may increase the risk for bleeding.(1,2)

PREDISPOSING FACTORS: Bleeding risk may be increased in patients with creatinine clearance below 50 mL per minute(1-4). Use of multiple agents which increase edoxaban exposure or affect hemostasis would be expected to increase the risk for bleeding. The risk for bleeding episodes may be greater in patients with disease-associated factors (e.g. thrombocytopenia). Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs).

PATIENT MANAGEMENT: Management recommendations between approving regulatory agencies (FDA or European Medicines Agency, EMA) are conflicting. EMA approved prescribing information specifically states that dosage adjustments are not required solely for concomitant use with amiodarone, quinidine, or verapamil regardless of indication.(3,4) Potential interactions with azithromycin, clarithromycin, or oral itraconazole are not described.(3) FDA approved prescribing recommendations for edoxaban are indication specific:(2) - For prevention of stroke or embolic events due to nonvalvular atrial fibrillation, no edoxaban dose adjustments are recommended during concomitant therapy with P-glycoprotein inhibitors. - For treatment of deep vein thrombosis (DVT) or pulmonary embolism (PE), the edoxaban dose should be reduced to 30 mg daily during concomitant use with azithromycin, clarithromycin, oral itraconazole, quinidine or verapamil. The manufacturer of vimseltinib states concurrent use with P-gp substrates should be avoided. If concurrent use cannot be avoided, take vimseltinib at least 4 hours prior to edoxaban.(6) Monitor patients receiving anticoagulant therapy for signs of blood loss, including decreased hemoglobin and/or hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. When applicable, perform agent-specific laboratory test (e.g. anti Factor Xa inhibition) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. Discontinue edoxaban in patients with active bleeding. The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(9)

DISCUSSION: Edoxaban in vivo interaction studies have been performed for quinidine and verapamil. In vivo interaction studies have not been conducted for the remaining P-gp inhibitors linked to this monograph.(1,4) In an interaction study, the effect of repeat administration of quinidine (300 mg TID) on a single oral dose of edoxaban 60 mg was evaluated in healthy subjects. Both peak (Cmax) and total systemic exposure (AUC) to edoxaban and to the active M4 metabolite increased approximately 1.75-fold.(1) In an interaction study, the effect of repeat administration of verapamil (240 mg Verapamil SR Tablets (Calan SR) QD for 11 Days) on a single oral dose of edoxaban 60 mg on the morning of Day 10 was evaluated in healthy subjects. Total and peak systemic exposure to edoxaban increased 1.53-fold and 1.53-fold, respectively. Total and peak systemic exposure to the active M4 metabolite increased 1.31-fold and 1.28-fold, respectively.(1) Based upon the above results, patients in the DVT/PE trial had a 50% dose reduction (from 60 mg to 30 mg) during concomitant therapy with P-glycoprotein inhibitors. Approximately 0.5% of these patients required a dose reduction solely due to P-gp inhibitor use. This low rate of concurrent therapy was too small to allow for detailed statistical evaluation. Almost all of these patients were receiving quinidine or verapamil. In these patients, both trough edoxaban concentrations (Ctrough) used to evaluate bleeding risk, and total edoxaban exposure (AUC or area-under-curve) used to evaluate treatment efficacy, were lower than patients who did not require any edoxaban dose adjustment. In this DVT/PE comparator trial, subgroup analysis revealed that warfarin had numerically better efficacy than edoxaban in patients receiving P-gp inhibitors. Based upon the overall lower exposure to edoxaban in P-gp dose adjusted subjects, both EMA and FDA Office of Clinical Pharmacology (OCP) concluded that the edoxaban 50% dose reduction overcorrected for the difference in exposure.(1,4) Consequently, EMA recommended no edoxaban dose adjustments for patients receiving concomitant therapy with quinidine or verapamil.(3,4) A summary of pharmacokinetic interactions with edoxaban and verapamil concluded that if concurrent use is considered safe.(7) P-gp inhibitors linked to this interaction are: amiodarone, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, clarithromycin, cobicistat, conivaptan, daclatasvir, danicopan, daraxonrasib, daridorexant, diltiazem, diosmin, flibanserin, fostamatinib, ginseng, glecaprevir/pibrentasvir, hydroquinidine, imlunestrant, indinavir, oral itraconazole, ivacaftor, josamycin, ledipasvir, lonafarnib, mavorixafor, neratinib, osimertinib, pirtobrutinib, posaconazole, propafenone, quinidine, ranolazine, selpercatinib, sotorasib, telaprevir, telithromycin, tezacaftor, tepotinib, tucatinib, valbenazine, velpatasvir, vemurafenib, vepdegestrant, verapamil, vimseltinib, and voclosporin.(8)

Select P-Gp Inhibitors/Edoxaban (> 30 Mg)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Edoxaban is a substrate for P-glycoprotein (P-gp). Inhibitors of P-gp may increase intestinal absorption and decrease renal tubular elimination of edoxaban.(1,2)

CLINICAL EFFECTS: Concurrent use with selected P-gp inhibitors may result in higher systemic concentrations of edoxaban which may increase the risk for bleeding.(1,2)

PREDISPOSING FACTORS: Bleeding risk may be increased in patients with creatinine clearance below 50 mL per minute(1-4). Use of multiple agents which increase edoxaban exposure or affect hemostasis would be expected to increase the risk for bleeding. The risk for bleeding episodes may be greater in patients with disease-associated factors (e.g. thrombocytopenia). Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs).

PATIENT MANAGEMENT: Management recommendations between approving regulatory agencies (FDA or European Medicines Agency, EMA) are conflicting. EMA approved prescribing information specifically states that dosage adjustments are not required solely for concomitant use with amiodarone, quinidine, or verapamil regardless of indication.(3,4) Potential interactions with azithromycin, clarithromycin, or oral itraconazole are not described.(3) FDA approved prescribing recommendations for edoxaban are indication specific:(2) - For prevention of stroke or embolic events due to nonvalvular atrial fibrillation, no edoxaban dose adjustments are recommended during concomitant therapy with P-glycoprotein inhibitors. - For treatment of deep vein thrombosis (DVT) or pulmonary embolism (PE), the edoxaban dose should be reduced to 30 mg daily during concomitant use with azithromycin, clarithromycin, oral itraconazole, quinidine or verapamil. The manufacturer of vimseltinib states concurrent use with P-gp substrates should be avoided. If concurrent use cannot be avoided, take vimseltinib at least 4 hours prior to edoxaban.(6) Monitor patients receiving anticoagulant therapy for signs of blood loss, including decreased hemoglobin and/or hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. When applicable, perform agent-specific laboratory test (e.g. anti Factor Xa inhibition) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. Discontinue edoxaban in patients with active bleeding. The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(9)

DISCUSSION: Edoxaban in vivo interaction studies have been performed for quinidine and verapamil. In vivo interaction studies have not been conducted for the remaining P-gp inhibitors linked to this monograph.(1,4) In an interaction study, the effect of repeat administration of quinidine (300 mg TID) on a single oral dose of edoxaban 60 mg was evaluated in healthy subjects. Both peak (Cmax) and total systemic exposure (AUC) to edoxaban and to the active M4 metabolite increased approximately 1.75-fold.(1) In an interaction study, the effect of repeat administration of verapamil (240 mg Verapamil SR Tablets (Calan SR) QD for 11 Days) on a single oral dose of edoxaban 60 mg on the morning of Day 10 was evaluated in healthy subjects. Total and peak systemic exposure to edoxaban increased 1.53-fold and 1.53-fold, respectively. Total and peak systemic exposure to the active M4 metabolite increased 1.31-fold and 1.28-fold, respectively.(1) Based upon the above results, patients in the DVT/PE trial had a 50% dose reduction (from 60 mg to 30 mg) during concomitant therapy with P-glycoprotein inhibitors. Approximately 0.5% of these patients required a dose reduction solely due to P-gp inhibitor use. This low rate of concurrent therapy was too small to allow for detailed statistical evaluation. Almost all of these patients were receiving quinidine or verapamil. In these patients, both trough edoxaban concentrations (Ctrough) used to evaluate bleeding risk, and total edoxaban exposure (AUC or area-under-curve) used to evaluate treatment efficacy, were lower than patients who did not require any edoxaban dose adjustment. In this DVT/PE comparator trial, subgroup analysis revealed that warfarin had numerically better efficacy than edoxaban in patients receiving P-gp inhibitors. Based upon the overall lower exposure to edoxaban in P-gp dose adjusted subjects, both EMA and FDA Office of Clinical Pharmacology (OCP) concluded that the edoxaban 50% dose reduction overcorrected for the difference in exposure.(1,4) Consequently, EMA recommended no edoxaban dose adjustments for patients receiving concomitant therapy with quinidine or verapamil.(3,4) A summary of pharmacokinetic interactions with edoxaban and verapamil concluded that if concurrent use is considered safe.(7) P-gp inhibitors linked to this interaction are: amiodarone, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, clarithromycin, cobicistat, conivaptan, daclatasvir, danicopan, daraxonrasib, daridorexant, diltiazem, diosmin, flibanserin, fostamatinib, ginseng, glecaprevir/pibrentasvir, hydroquinidine, imlunestrant, indinavir, oral itraconazole, ivacaftor, josamycin, ledipasvir, lonafarnib, neratinib, osimertinib, pirtobrutinib, posaconazole, propafenone, quinidine, ranolazine, selpercatinib, sotorasib, telaprevir, telithromycin, tezacaftor, tepotinib, tucatinib, valbenazine, velpatasvir, vemurafenib, vepdegestrant, verapamil, vimseltinib, and voclosporin.(8)

Selected Hepatitis C Agents/Digoxin

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Ledipasvir,(1) ombitasvir-paritaprevir-ritonavir,(2,3) velpatasvir(4,5), and glecaprevir-pibrentasvir (8) inhibit intestinal P-glycoprotein (P-gp) transport, which may increase digoxin bioavailability. Glecaprevir-pibrentasvir also inhibits OATP1B3.

CLINICAL EFFECTS: Concurrent use of ledipasvir,(1) or ombitasvir-paritaprevir-ritonavir,(2,3) or velpatasvir,(4,5) or glecaprevir-pibrentasvir may result in elevated levels and toxicity from digoxin. Symptoms of digoxin toxicity can include anorexia, nausea, vomiting, headache, fatigue, malaise, drowsiness, generalized muscle weakness, disorientation, hallucinations, visual disturbances, and arrhythmias.

PREDISPOSING FACTORS: Low body weight, advanced age, impaired renal function, hypokalemia, hypercalcemia, and/or hypomagnesemia may increase the risk of digoxin toxicity.

PATIENT MANAGEMENT: Monitor patients receiving concurrent therapy with ledipasvir for elevated digoxin levels and adjust the dose accordingly.(1) The manufacturer of ombitasvir-paritaprevir-ritonavir recommends a digoxin dose reduction of 30-50% with follow-up digoxin monitoring in patients not also receiving concomitant dasabuvir therapy.(2) In contrast, monitoring but no automatic dose adjustment is recommended in patients receiving ombitasvir-paritaprevir-ritonavir with dasabuvir.(2,3) During concomitant therapy, the manufacturer of sofosbuvir-velpatasvir recommends digoxin therapeutic concentration monitoring and digoxin dose adjustment based upon digoxin prescribing information modifications for concentration increases less than 50%.(4) During concomitant therapy, the manufacturer of sofosbuvir-velpatasvir-voxilaprevir recommends digoxin therapeutic concentration monitoring and digoxin dose adjustment based upon digoxin prescribing information modifications for concentration increases with unclear magnitude.(5) The manufacture of glecaprevir-pibrentasvir recommends a digoxin dose reduction of 50% or modification of the dosing frequency with follow-up digoxin monitoring in patients.(8)

DISCUSSION: In an interaction study, the combination of ombitasvir-paritaprevir-ritonavir increased exposure (area-under-curve, AUC) to a single dose of digoxin by 36% (range: 21 - 54%).(2) In a second evaluation, the combination of ombitasvir-paritaprevir-ritonavir and dasabuvir with digoxin increased digoxin 16% (range: 9 - 23%).(6) In an interaction study in 21 subjects, velpatasvir (100 mg) increased the Cmax and AUC of digoxin (0.25 mg single dose) by 88% and 34%, respectively.(4,5) Concomitant administration of ritonavir and digoxin increased the digoxin AUC 86%.(7) In an interaction study in 12 subjects, glecaprevir-pibrentasvir (400/120 mg daily) increased the Cmax and AUC of digoxin (0.5 mg single dose) by 72% and 48%, respectively.(8)

Selected P-Glycoprotein (P-Gp) Inhibitors/Betrixaban

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Betrixaban is a substrate for the P-glycoprotein (P-gp) system. Inhibition of intestinal P-gp leads to increased absorption of betrixaban.(1)

CLINICAL EFFECTS: The concurrent use betrixaban with P-gp inhibitors may lead to elevated plasma levels of betrixaban, increasing the risk for bleeding.

PREDISPOSING FACTORS: Factors associated with an increased risk for bleeding include renal impairment, concomitant use of P-gp inhibitors, coexisting conditions (e.g. recent trauma) or use of drugs (e.g. NSAIDs) associated with bleeding risk, and patient weight < 50 kg.(1)

PATIENT MANAGEMENT: Assess renal function and evaluate patient for other pre-existing risk factors for bleeding prior to initiating concurrent therapy. The concurrent use of betrixaban and P-gp inhibitors should be avoided in patients with severe renal impairment (CrCl less than 30 ml/min).(1) The recommended dose for patients receiving or starting concomitant P-gp inhibitors is an initial single dose of 80 mg followed by 40 mg once daily. The recommended duration of treatment is 35 to 42 days.(1) Note that if betrixaban is used with the combination of darunavir and cobicistat, dose adjustment of betrixaban is not necessary.(2) The manufacturer of vimseltinib states concurrent use with P-gp substrates should be avoided. If concurrent use cannot be avoided, take vimseltinib at least 4 hours prior to betrixaban.(3) Careful monitoring for signs and symptoms of bleeding is warranted during concurrent therapy. Consider regular monitoring of hemoglobin, platelet levels, and/or activated partial thromboplastin time (aPTT) or ecarin clotting time (ECT). Instruct patients to report any signs and symptoms of bleeding, such as bleeding from the eyes, gums or nose; unusual bruising; dark stools; red or dark brown urine; and/or abdominal pain or swelling.(1) The anticoagulant effect of betrixaban is expected to persist for at least 72 hours after the last dose. The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(8)

DISCUSSION: In the APEX randomized, double-blind study the incidence of major or clinically relevant non-major bleeds (CRNM) in the betrixaban 40mg and 80 mg group was higher in patients taking concomitant P-gp inhibitors (2.8% vs. 4.1% vs. 4.7%).(4) In a study in 12 subjects, concomitant administration of a single dose of betrixaban (40 mg) following a 5-day regimen of ketoconazole (200 mg twice daily) resulted in an increase in betrixaban's maximum concentration (Cmax) and area-under-the-curve (AUC) of 2.3-fold and 2.3-fold, respectively.(5) An open-label study looking at concomitant administration of a single dose of betrixaban with verapamil in 18 subjects found an increase in betrixaban's Cmax and AUC of approximately 4.7-fold and 3-fold, respectively.(5) In a study, concomitant administration of betrixaban (80 mg) with amiodarone resulted in an increase in betrixaban's Cmax by 143%.(5) A summary of pharmacokinetic interactions with betrixaban and amiodarone, diltiazem, or verapamil concluded that if concurrent use is warranted, the betrixaban dose should be reduced to 80 mg once then 40 mg daily. Use should be avoided if CrCl is less than 30 ml/min.(6) P-gp inhibitors include asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, clarithromycin, cobicistat, conivaptan, cyclosporine, daclatasvir, danicopan, daraxonrasib, daridorexant, diltiazem, diosmin, dronedarone, erythromycin, flibanserin, fostamatinib, ginseng, glecaprevir, hydroquinidine, imlunestrant, indinavir, itraconazole, ivacaftor, josamycin, lapatinib, ledipasvir, lonafarnib, lopinavir, mavorixafor, neratinib, osimertinib, pibrentasvir, pirtobrutinib, posaconazole, propafenone, quinidine, ranolazine, ritonavir, selpercatinib, sofosbuvir/velpatasvir/voxilaprevir, sotorasib, telaprevir, telithromycin, tepotinib, tezacaftor, tucatinib, valbenazine, velpatasvir, vemurafenib, vepdegestrant, vimseltinib, voclosporin and voxilaprevir.(1,4-7)

Slt Direct-Acting Antiviral/Slt Anticoagulants (Vit K Antag)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: The exact mechanism is unknown. Warfarin sensitivity may be decreased during concurrent therapy with direct-acting antivirals. Improved hepatic function as a result of successful treatment of Hepatitis C may also play a role.

CLINICAL EFFECTS: Use of direct-acting antivirals in the treatment of Hepatitis C may result in decreased warfarin effects, which may increase the risk of thrombosis.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Monitor INR response closely in patients maintained on warfarin during treatment with direct-acting antivirals. Consider more frequent monitoring of INR during concurrent therapy and after the completion of therapy with direct-acting antivirals until a stable warfarin dose is established.

DISCUSSION: In a clinical study of 43 patients treated with elbasvir-grazoprevir, the warfarin sensitivity index (WSI) (steady state INR/mean daily warfarin dose) decreased from 0.53 +/- 0.25 to 0.4 +/- 0.22 at treatment completion with elbasvir-grazoprevir which represents a 25.2% decrease. Twelve weeks after treatment completion the WSI returned to 0.51 +/- 0.28. Mean weekly warfarin dose requirement increased over the course of therapy, from 40.3 +/- 22.0 mg to 44.6 +/- 23.4 mg, and returned to near original warfarin dose requirement after therapy at 46 mg. Time in therapeutic range for INR dropped from 74.1% to 39.8% during treatment and returned to 64.9% after treatment.(1) In a retrospective review of patients treated with either ombitasvir-paritaprevir-ritonavir-dasabuvir or sofosbuvir, the warfarin sensitivity index (steady state INR/mean daily warfarin dose) decreased 23% during therapy. The percentage of subtherapeutic INRs increased from 28% prior to treatment to 58% during treatment.(2) Pharmacokinetic studies found no significant effects on warfarin from either ombitasvir-paritaprevir-ritonavir(3) or ombitasvir-paritaprevir-ritonavir-dasabuvir.(4) There have been case reports of decreased warfarin effects and increased warfarin dosage requirements during the treatment of Hepatitis C with: ombitasvir-paritaprevir-ritonavir-dasabuvir,(5) sofosbuvir,(6) sofosbuvir-ledipasvir,(7) and sofosbuvir-velpatasvir.(8) There is a case report of decreased INR following the addition of ombitasvir-paritaprevir-ritonavir-dasabuvir to acenocoumarol.(9)

If the fixed combination of ledipasvir and sofosbuvir (ledipasvir/sofosbuvir) is used in conjunction with ribavirin, the contraindications to ribavirin also apply. (See Precautions Related to Fixed Combinations and Multiple-drug Treatment Regimens under Warnings/Precautions: Other Warnings/Precautions, in Cautions.)

There are no contraindication contraindications for this drug.

There are no severe contraindications for this drug.

• Hypoglycemic disorder
• Reactivation of hepatitis B

Ledipasvir/sofosbuvir: Adverse effects reported in 5% or more of patients receiving ledipasvir/sofosbuvir include fatigue, headache, nausea, diarrhea, abdominal pain, insomnia or sleep disorder, irritability, rash, pruritus, dry skin, arthralgia, myalgia, back pain, asthenia, cough, upper respiratory tract infection, and dizziness.

Ledipasvir/sofosbuvir in conjunction with ribavirin: Adverse effects reported in 5% or more of patients receiving ledipasvir/sofosbuvir in conjunction with ribavirin include fatigue, headache, nausea, diarrhea, insomnia, asthenia, cough, bronchitis, dyspnea, irritability, pruritus, dry skin, myalgia, and decreased hemoglobin.

Rare or Very Rare

• Acute occlusion of mesenteric vein
• Angioedema
• Dysglycemia
• Gout
• Hypertension
• Reactivation of hepatitis B
• Urinary retention

More Frequent

• Fatigue
• General weakness
• Headache disorder
• Nausea

Less Frequent

• Diarrhea
• Dizziness
• Hyperbilirubinemia
• Insomnia

Rare or Very Rare

• Abdominal distension
• Acne vulgaris
• Acute abdominal pain
• Alopecia
• Anorexia
• Arthralgia
• Blistering skin
• Bruising
• Conjunctivitis
• Constipation
• Depression
• Disturbance of attention
• Edema
• Erectile dysfunction
• Gastroesophageal reflux disease
• Hyperhidrosis
• Irritability
• Libido changes
• Muscle spasm
• Muscle weakness
• Nasal congestion
• Pain in oropharynx
• Palpitations
• Pruritus of skin
• Salpingitis
• Sinusitis
• Skin rash
• Sleep disorder
• Sprains and strains
• Symptoms of anxiety
• Visual changes
• Vomiting
• Weight loss

No enhanced messaging available.

Safety and efficacy of ledipasvir/sofosbuvir have not been established in pediatric patients younger than 3 years of age.

Safety and efficacy of ledipasvir/sofosbuvir for the treatment of HCV genotype 1 or 4 infection in treatment-naive and previously treated pediatric patients 3 years of age or older without cirrhosis or with compensated cirrhosis (Child-Pugh class A) have been established in an open-label clinical study.

Safety and efficacy of ledipasvir/sofosbuvir for the treatment of HCV genotype 1 infection in pediatric patients 3 years of age or older with decompensated cirrhosis (Child-Pugh class B or C) and for the treatment of HCV genotype 1 or 4 infection in pediatric patients 3 years of age or older who are liver transplant recipients without cirrhosis or with compensated cirrhosis (Child-Pugh class A) are supported by pharmacokinetic data indicating that ledipasvir, sofosbuvir, and GS-331007 exposures in pediatric patients 3 years of age or older with HCV genotype 1, 3, or 4 infection are similar to exposures in adults.

Safety and efficacy of ledipasvir/sofosbuvir for the treatment of HCV genotype 5 or 6 infection in pediatric patients 3 years of age or older are supported by pharmacokinetic data indicating that ledipasvir, sofosbuvir, and GS-331007 exposures in pediatric patients 3 years of age or older with HCV genotype 1, 3, or 4 infection are similar to exposures in adults.

Adverse effects of ledipasvir/sofosbuvir reported in pediatric patients 3 years of age and older are similar to those observed in adults.

Data are not available regarding the safety and pharmacokinetics of ledipasvir/sofosbuvir in pediatric patients with renal impairment.

Adequate data are not available regarding use of ledipasvir/sofosbuvir in pregnant women. In animal studies, neither ledipasvir nor sofosbuvir affected fetal development at the dosages tested.

When ledipasvir/sofosbuvir is used in conjunction with ribavirin, clinicians should consider that ribavirin may cause fetal toxicity and/or death and extreme care must be taken to avoid pregnancy in female patients and in female partners of male patients receiving the ribavirin-containing regimen. (See Cautions: Pregnancy, Fertility, and Lactation, in Ribavirin 8:18.32.)

It is not known whether ledipasvir, sofosbuvir, or their metabolites are distributed into human milk, affect milk production, or have effects on a breast-fed child.

The predominant metabolite of sofosbuvir (GS-331007) is distributed into milk in rats, and ledipasvir has been detected in plasma of suckling rat pups. Ledipasvir and GS-331007 had no apparent effects on the nursing pups.

The benefits of breast-feeding and the importance of ledipasvir/sofosbuvir to the woman should be considered along with the potential adverse effects on the breast-fed child from the drug or from the underlying maternal condition.

When ledipasvir/sofosbuvir is used in conjunction with ribavirin, the potential for adverse reactions to ribavirin in nursing infants should be considered. (See Precautions Related to Fixed Combinations and Multiple-drug Treatment Regimens under Warnings/Precautions: Other Warnings/Precautions, in Cautions.)

Ledipasvir/sofosbuvir dosage adjustments are not necessary in geriatric patients.

No overall differences in safety and efficacy of ledipasvir/sofosbuvir have been observed between patients 65 years of age and older and younger adults. However, greater sensitivity in some older individuals cannot be ruled out.