Acid Controller (famotidine)

In patients with renal impairment, doses and/or frequency of administration of famotidine can be modified in response to the degree of renal impairment. Adverse CNS effects have been reported in patients with moderate or severe renal insufficiency receiving famotidine, and modification of dosage and/or dosing interval may be used to avoid excess accumulation of the drug in such patients. In adults with moderate (creatinine clearances less than 50 mL/minute) or severe (creatinine clearances less than 10 mL/minute) renal impairment, the manufacturer states that dosage of famotidine may be reduced to half the usual dosage or the dosing interval may be prolonged to 36-48 hours as necessary according to the patient's clinical response. Some clinicians have recommended that one-half the usual adult dosage be administered in adults with creatinine clearances of 30-60 mL/minute per 1.48 m2 and that one-fourth the usual adult dosage be administered in those with creatinine clearances less than 30 mL/minute per 1.48 m2.

Based on the comparison of pharmacokinetic parameters of famotidine in adults and children, dosage adjustment also should be considered in children with moderate or severe renal impairment.

No dosing information is available for this tab.

There is no enhanced messaging for this drug.

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

Cyp1a2 Inhibitors/Fezolinetant

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 CYP1A2 may inhibit the metabolism of fezolinetant.(1-4)

CLINICAL EFFECTS: Concurrent use of a CYP1A2 inhibitor may increase levels of and adverse effects from fezolinetant.(1-4)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Recommendations for concurrent use of fezolinetant with CYP1A2 inhibitors differ in different regions. The US manufacturer of fezolinetant states that concurrent use with strong, moderate, and weak CYP1A2 inhibitors is contraindicated.(1) The Australian, Canadian, and UK manufacturers of fezolinetant state that concurrent use with strong and moderate CYP1A2 inhibitors is contraindicated, while weak CYP1A2 inhibitors are not predicted to cause clinically relevant changes in fezolinetant exposure.(2-4)

DISCUSSION: In a study, fluvoxamine, a strong CYP1A2 inhibitor, increased fezolinetant maximum concentration (Cmax) and area-under-curve (AUC) by 80% and 840%, respectively. Mexiletine (400 mg every 8 hours), a moderate CYP1A2 inhibitor, increased fezolinetant Cmax and AUC by 40% and 360%, respectively. Cimetidine (300 mg every 6 hours), a weak CYP1A2 inhibitor, increased fezolinetant Cmax and AUC by 30% and 100%, respectively.(1) Strong CYP1A2 inhibitors linked to this monograph include angelica root, ciprofloxacin, enasidenib, enoxacin, fluvoxamine, and rofecoxib. Moderate CYP1A2 inhibitors linked to this monograph include capmatinib, centanafadine, dipyrone, fexinidazole, genistein, hormonal contraceptives, methoxsalen, mexiletine, osilodrostat, phenylpropanolamine, pipemidic acid, rucaparib, troleandomycin, vemurafenib, and viloxazine. Weak CYP1A2 inhibitors linked to this monograph include acyclovir, allopurinol, artemisinin, belumosudil, caffeine, cannabidiol, cimetidine, curcumin, dan-shen, deferasirox, disulfiram, Echinacea, famotidine, ginseng, norfloxacin, obeticholic acid, parsley, piperine, propafenone, propranolol, ribociclib, simeprevir, thiabendazole, ticlopidine, triclabendazole, valacyclovir, verapamil, and zileuton.(5-7)

H2 Antagonists/Olverembatinib

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: The aqueous solubility of olverembatinib is pH dependent. Higher gastric pH leads to lower solubility which may reduce olverembatinib absorption.(1)

CLINICAL EFFECTS: Coadministration of H2 receptor antagonists may reduce the bioavailability of olverembatinib leading to decreased systemic levels and effectiveness.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of olverembatinib states that concurrent use with H2 receptor antagonists should be avoided.(1)

DISCUSSION: Olverembatinib has pH-dependent solubility.(1)

H2 Antagonists; Proton Pump Inhibit/Posaconazole Suspension

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: H2 antagonists and proton pump inhibitors (PPIs) increase the stomach pH, possibly reducing gastrointestinal absorption of posaconazole suspension.

CLINICAL EFFECTS: Concurrent use of H2 antagonists or proton pump inhibitors (PPIs) may result in decreased effectiveness of posaconazole suspension.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid the concurrent use of posaconazole suspension with H2 antagonists or proton pump inhibitors (PPIs).(1) If H2 antagonists or PPI therapy is required, use the tablet formulation or powder mix formulation of posaconazole.

DISCUSSION: Concurrent cimetidine (400 mg twice daily) decreased both posaconazole (200 mg daily) maximum concentration (Cmax) and area-under-curve (AUC) levels by 39%.(1) No significant effects with other H2 blockers have been noted.(1) Esomeprazole (40 mg daily for 3 days) decreased the Cmax and AUC of a single dose of posaconazole suspension (400 mg) by 46% and 32%, respectively.(1) In a study of posaconazole levels in patients with acute myeloid leukemia or myelodysplastic syndrome, use of pantoprazole was associated with decreased posaconazole levels.(3) In a cross-over study in 5 healthy subjects, esomeprazole decreased the Cmax and AUC of posaconazole suspension by 37% and 84%, respectively. Simultaneous intake of Coca-Cola did not completely counteract the effects of esomeprazole.(4) In a study in healthy subjects, esomeprazole decreased the Cmax and AUC of posaconazole suspension by 55% and 49%, respectively. Simultaneous intake of Coca-Cola did not completely counteract the effects of esomeprazole.(5)

H2 Antagonists; Proton Pump Inhibitors/Defactinib

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: The aqueous solubility of defactinib is pH dependent. Higher gastric pH leads to lower solubility which may reduce defactinib absorption.(1)

CLINICAL EFFECTS: Coadministration of H2 antagonists or proton pump inhibitors (PPIs) may reduce the bioavailability of defactinib, leading to decreased systemic levels and effectiveness.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of defactinib states that concurrent use with H2 antagonists or proton pump inhibitors should be avoided.(1) If concurrent use with an acid-reducing agent cannot be avoided, administer defactinib 2 hours before or 2 hours after the administration of a locally acting antacid.(1)

DISCUSSION: In an interaction study, defactinib area-under-the-curve (AUC) decreased by 79% and maximum concentration (Cmax) decreased by 85% following concomitant use of multiple doses of omeprazole 40 mg daily. The AUC and Cmax of N-desmethyl amide (M4), a major metabolite of defactinib, decreased by 83% and 88%, respectively.(1)

H2 Antagonists; Proton Pump Inhibitors/Levoketoconazole

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: The aqueous solubility of levoketoconazole is pH dependent. Higher gastric pH leads to lower solubility. H2-receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) increase gastric pH and may decrease the absorption of levoketoconazole.(1)

CLINICAL EFFECTS: Coadministration of H2RAs or PPIs may reduce the bioavailability of levoketoconazole, leading to decreased systemic levels and effectiveness.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Coadministration of levoketoconazole with PPIs and H2RAs should be avoided.(1)

DISCUSSION: Levoketoconazole is very slightly soluble in water but soluble below pH 2. H2RAs and PPIs raise gastric pH and may impair dissolution and absorption of levoketoconazole.(1)

H2 Antagonists; Proton Pump Inhibitors/Nirogacestat

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: The aqueous solubility of nirogacestat is pH dependent. Higher gastric pH leads to lower solubility which may reduce nirogacestat absorption.(1)

CLINICAL EFFECTS: Coadministration of proton pump inhibitors (PPIs) or H2 antagonists may reduce the bioavailability of nirogacestat, leading to decreased systemic levels and effectiveness.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Coadministration of nirogacestat with proton pump inhibitors, H2 antagonists, and antacids should be avoided. If coadministration with an acid-reducing agent is unavoidable, take nirogacestat 2 hours before or 2 hours after a locally acting antacid.(1)

DISCUSSION: The solubility of nirogacestat is poor at a pH >= 6.(1) Concomitant use of proton pump inhibitors, H2 antagonists, or antacids are expected to reduce concentrations of nirogacestat.(1)

H2 Antagonists; Proton Pump Inhibitors/Secretin

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: H2 antagonists and proton pump inhibitors (PPIs) may result in an incorrect secretin stimulation test result.(1)

CLINICAL EFFECTS: Concurrent use of H2 antagonists and proton pump inhibitors (PPIs) may impact the accuracy of the secretin stimulation test.(1)

PREDISPOSING FACTORS: Patients with alcoholic or other liver disease may be hyperresponsive to stimulation with a secretin stimulation test, masking the presence of coexisting pancreatic disease. Consider additional testing and clinical assessment for diagnosis.(1)

PATIENT MANAGEMENT: The US manufacturer of human secretin states concurrent use of H2 antagonists and proton pump inhibitors (PPIs) at the time of stimulation testing may cause the patient to be hyperresponsive to secretin stimulation and suggest false gastrinoma results. The manufacturer recommends discontinuing H2 antagonists at least 2 days prior to testing. The US manufacturer of vonoprazan recommends stopping vonoprazan at least 4 weeks prior to testing.(2-3) Consult prescribing information for PPIs before administering prior to a secretin stimulation test.(1)

DISCUSSION: Concurrent use of H2 antagonists and proton pump inhibitors (PPIs) may impact the accuracy of the secretin stimulation test.(1)

H2 Antagonists; Proton Pump Inhibitors/Sotorasib

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: The aqueous solubility of sotorasib is pH dependent. Higher gastric pH leads to lower solubility which may reduce sotorasib absorption.(1)

CLINICAL EFFECTS: Coadministration of proton pump inhibitors (PPIs) or H2 antagonists may reduce the bioavailability of sotorasib, leading to decreased systemic levels and effectiveness.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Coadministration of sotorasib with proton pump inhibitors, H2 antagonists, and antacids should be avoided. If coadministration with an acid-reducing agent is unavoidable, take sotorasib 4 hours before or 10 hours after a locally acting antacid.(1) The UK manufacturer of sotorasib states if co-administration with an acid-reducing agent (such as a PPI or an H2 antagonist) is required, sotorasib should be taken with an acidic beverage (such as cola). Alternatively, sotorasib should be taken 4 hours before or 10 hours after administration of a local antacid.(2)

DISCUSSION: The solubility of sotorasib in the aqueous media decreases over the range pH 1.2 to 6.8 from 1.3 mg/mL to 0.03 mg/mL. In an interaction study, coadministration of repeat doses of omeprazole with a single dose of sotorasib decreased sotorasib maximum concentration (Cmax) by 65% and area-under-curve (AUC) by 57% under fed conditions, and decreased sotorasib Cmax by 57% and AUC by 42% under fasted conditions. Under fasted conditions, co-administration of repeat doses of omeprazole with a single dose of sotorasib and 240ml of an acidic beverage (non-diet cola) decreased sotorasib Cmax by 32% and AUC by 23%. The UK manufacturer of sotorasib states the clinical relevance of the decreased sotorasib exposure when co-administered with omeprazole and cola is unclear and sotorasib efficacy might be reduced.(2) Coadministration of a single dose of famotidine given 10 hours prior to and 2 hours after a single dose of sotorasib under fed conditions decreased sotorasib Cmax by 35% and AUC by 38%.(1)

H2 Antagonists; Proton Pump Inhibitors/Taletrectinib

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: The aqueous solubility of taletrectinib is pH dependent. Higher gastric pH leads to lower solubility which may reduce taletrectinib absorption.(1)

CLINICAL EFFECTS: Coadministration of H2 antagonists or proton pump inhibitors (PPIs) may reduce the bioavailability of taletrectinib, leading to decreased systemic levels and effectiveness.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of taletrectinib states that concurrent use with H2 antagonists or proton pump inhibitors should be avoided.(1) If concurrent use with an acid-reducing agent cannot be avoided, administer taletrectinib 2 hours before or 2 hours after the administration of a locally acting antacid.(1)

DISCUSSION: In an interaction study, taletrectinib area-under-the-curve (AUC) decreased by 40% and maximum concentration (Cmax) decreased by 65% following concomitant use of omeprazole 40 mg daily.(1)

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

Cimetidine; Famotidine/Tizanidine

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

MECHANISM OF ACTION: Cimetidine and famotidine may inhibit the metabolism of tizanidine by CYP1A2.(1)

CLINICAL EFFECTS: Concurrent use of cimetidine or famotidine may result in elevated levels of and effects from tizanidine, including hypotension, bradycardia, drowsiness, sedation, and decreased psychomotor function.

PREDISPOSING FACTORS: The risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(2)

PATIENT MANAGEMENT: The US manufacturer of tizanidine states that concurrent use of tizanidine with inhibitors of CYP1A2, such as cimetidine or famotidine, should be avoided. If concurrent use is warranted, tizanidine should be initiated with 2 mg dose and increased in 2-4 mg steps daily based on patient response to therapy.(1) If adverse reactions such as hypotension, bradycardia, or excessive drowsiness occur, reduce or discontinue tizanidine therapy.(1)

DISCUSSION: In a study in 10 healthy subjects, concurrent fluvoxamine, another inhibitor of CYP1A2, increased tizanidine maximum concentration (Cmax), area-under-curve (AUC), and half-life (T1/2) by 12-fold, 33-fold, and 3-fold, respectively. Significant decreases in blood pressure and increases in drowsiness and psychomotor impairment occurred.(1) In a study in 10 healthy subjects, concurrent ciprofloxacin, another inhibitor of CYP1A2, increase tizanidine Cmax and AUC by 7-fold and 10-fold, respectively. Significant decreases in blood pressure and and increases in drowsiness and psychomotor impairment occurred.(1)

H2 Antagonists/Dasatinib; Pazopanib

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

MECHANISM OF ACTION: The solubility of dasatinib(1) and pazopanib(2) is pH dependent. Changes in gastric pH from H2 antagonists may decrease the absorption of dasatinib(1) and pazopanib.(2)

CLINICAL EFFECTS: Use of H2 antagonists may result in decreased levels and effectiveness of dasatinib(1) and pazopanib.(2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid the use of H2-antagonists and proton pump inhibitors (PPIs) in patients receiving treatment with dasatinib(1) or pazopanib.(2) Consider the use of short-acting antacids in these patients.(1) If antacids are used, separate the administration times by at least two hours for dasatinib(1) and several hours for pazopanib.(2) The manufacturer of Phyrago states that it can be administered with gastric acid reducing agents. Administration times should be separated with antacids.(3)

DISCUSSION: In a study in 24 healthy subjects, administration of a single dose of dasatinib (50 mg) 10 hours after famotidine decreased dasatinib area-under-curve (AUC) and maximum concentration (Cmax) by 61% and 63%, respectively.(1) In a study in 14 healthy subjects, administration of a single dose of dasatinib (100 mg) 22 hours after omeprazole (40 mg at steady state) decreased dasatinib AUC and Cmax by 43% and 42%, respectively.(1) In a study in 24 healthy subjects, simultaneous administration of dasatinib (50 mg) with aluminum hydroxide/magnesium hydroxide (30 ml) decreased dasatinib AUC and Cmax by 55% and 58%, respectively. In the same subjects, administration of the antacid 2 hours before dasatinib decreased dasatinib Cmax by 26%, but had no effect on dasatinib AUC.(1) In a study in 13 patients, esomeprazole (40 mg daily for 5 days) decreased the Cmax and AUC of pazopanib (400 mg daily) by 42% and 40%, respectively, when compared to the administration of pazopanib alone.(2) Phyrago is not sensitive to increased gastric pH due to its polymer formulation. No clinically significant pharmacokinetic changes were seen with concurrent administration of Phyrago with omeprazole (proton pump inhibitor) or famotidine (H2 receptor antagonist).(3)

H2 Antagonists/Ziftomenib

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

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

CLINICAL EFFECTS: Coadministration of H2 receptor antagonists may reduce the bioavailability of ziftomenib, leading to decreased systemic levels and effectiveness.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of ziftomenib states that concurrent use with H2 antagonists should be avoided.(1) If concurrent use cannot be avoided, administer ziftomenib 2 hours before or 10 hours after the administration of an H2 receptor antagonist.(1)

DISCUSSION: The impact of H2 receptor antagonists on the pharmacokinetics of ziftomenib has not been investigated in clinical studies. In an interaction study, coadministration of proton pump inhibitors (PPIs) decreased ziftomenib area-under-the-curve (AUC) by 53% and maximum concentration (Cmax) by 70%.(1)

H2 Antagonists;Proton Pump Inhibitors/Methylphenidate Xr-Odt

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

MECHANISM OF ACTION: The solubility of methylphenidate extended release orally disintegrating tablets (XR-ODT) is pH-dependent. At elevated pH, methylphenidate may be released from the tablets more quickly, resulting in increased absorption.(1)

CLINICAL EFFECTS: Coadministration of H2 antagonists or proton pump inhibitors (PPIs) may result in an altered pharmacokinetic profile of methylphenidate XR-ODT, which may change the effectiveness and/or adverse effects of methylphenidate XR-ODT.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Coadministration of methylphenidate XR-ODT with H2 antagonists or PPIs is not recommended.(1,2)

DISCUSSION: In in vitro studies, when media pH was increased from 1.2 to 6.8, percentage release of methylphenidate from the XR-ODT tablet was increased by 67% at 0.5 hours, and by 93% at 2.5 hours. The increased dissolution of methylphenidate at higher pH may result in increased drug absorption and change the concentration-time profile of methylphenidate, which is correlated with pharmacological effect.(1)

Long Acting Antacids; H2s;Ppis/Selected Cephalosporins

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

MECHANISM OF ACTION: Absorption of oral cefpodoxime or cefuroxime may be reduced in patients receiving concomitant treatment with acid reducing agents.(1-5)

CLINICAL EFFECTS: Antibiotic efficacy against organisms with a high minimum inhibitory concentration (MIC) to cefpodoxime or cefuroxime could be decreased.

PREDISPOSING FACTORS: Taking cefpodoxime or cefuroxime on an empty stomach magnifies this effect.

PATIENT MANAGEMENT: If possible, avoid the use of H2 antagonists and proton pump inhibitors(PPIs) in patients taking cefpodoxime or cefuroxime. If concurrent therapy is needed with antacids, H2 antagonists, or PPIs, administer cefpodoxime or cefuroxime after eating to maximize oral absorption. Some vitamin preparations may contain sufficient quantities of calcium and/or magnesium salts with antacid properties to interact as well.

DISCUSSION: In a study of ten subjects, administration of cefpodoxime after single dose famotidine 40 mg decreased both maximum concentration (Cmax) and area-under-curve (AUC) by approximately 40 percent compared with administration of cefpodoxime on an empty stomach.(3) In a study of 17 subjects, administration of cefpodoxime after single dose ranitidine 150 mg decreased Cmax and AUC by approximately 40 percent compared with administration of cefpodoxime on an empty stomach.(4) In a study performed prior to the introduction of PPIs, administration of ranitidine 300 mg and sodium bicarbonate followed by cefuroxime taken on a empty stomach lowered both Cmax and AUC of cefuroxime by approximately 40 per cent compared with administration of cefuroxime alone on an empty stomach. Postprandial administration of cefuroxime in subjects taking ranitidine was similar to that of subjects taking cefuroxime on an empty stomach.(5)

Selected H2 Antagonists/Infigratinib; Selpercatinib

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

MECHANISM OF ACTION: The solubility of infigratinib and selpercatinib is pH dependent. Changes in gastric pH from H2 antagonists may decrease the absorption of infigratinib and selpercatinib.(1,2)

CLINICAL EFFECTS: Use of H2 antagonists may result in decreased levels and effectiveness of infigratinib and selpercatinib.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid the use of H2 antagonists, proton pump inhibitors, and locally-acting antacids in patients receiving treatment with infigratinib or selpercatinib. If coadministration with H2 antagonists cannot be avoided, take infigratinib or selpercatinib at least 2 hours before or 10 hours after the H2 antagonist.(1,2) If the H2 antagonist is replaced with an antacid, take infigratinib or selpercatinib 2 hours before or 2 hours after the antacid.(1,2) If the H2 antagonist is replaced with a proton pump inhibitor, take selpercatinib with food.(2) Avoid taking proton pump inhibitors with infigratinib.(1)

DISCUSSION: Infigratinib is practically insoluble at pH 6.8.(1) In a study, ranitidine given 10 hours before and 2 hours after selpercatinib did not have a clinically significant effect on selpercatinib pharmacokinetics.(2)

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

Agents Affecting Gastric Ph/Itraconazole; Ketoconazole

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

MECHANISM OF ACTION: Antacids, buffers in didanosine products, H2 antagonists, and proton-pump inhibitors increase the stomach pH. Quinapril tablets may contain a high percentage of magnesium. Since some orally administered azole antifungal agents require an acidic medium for optimal absorption, agents may decrease the absorption of azole antifungal agents.

CLINICAL EFFECTS: Simultaneous administration of an antacid, buffered didanosine, a H2 antagonist, or a proton-pump inhibitor may result in decreased therapeutic effects of the azole antifungal.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If the concurrent administration of these two agents cannot be avoided, consider administering two capsules of glutamic acid hydrochloride 15 minutes before administering the antifungal and separate the administration times of the antifungal and the agent affecting gastric pH by at least two hours.

DISCUSSION: Itraconazole, ketoconazole, and posaconazole require an acidic medium for predictable dissolution and absorption decreases as pH increases and proton pump inhibitors are expected to decrease their absorption.(1-4) In a study in 11 healthy subjects, omeprazole (40 mg daily) decreased the maximum concentration (Cmax) and area-under-curve (AUC) of itraconazole (200 mg single dose) by 66% and 64%, respectively.(5) In a study in 15 healthy subjects, omeprazole (40 mg daily) had no effect on the pharmacokinetics of itraconazole solution.(6) In a study in 9 healthy subjects, omeprazole (60 mg) decreased the AUC of ketoconazole (200 mg single dose) by 83.4% compared to control (ketoconazole alone). Administration of Coca-Cola (240 ml) with ketoconazole and omeprazole raised ketoconazole AUC to 65% of control values.(7) Omeprazole has been shown to have no significant effect on the absorption of fluconazole(8) or voriconazole.(9) Case reports and in-vivo studies have documented significant decreases in ketoconazole levels during concurrent therapy with H-2 antagonists, including cimetidine and ranitidine. Concurrent administration of itraconazole and famotidine resulted in a significant decrease in itraconazole levels, but no significant changes in famotidine levels. An interaction should be expected to occur between both ketoconazole or itraconazole and the other H-2 antagonists.(10-14) In randomized, open-labeled, cross-over study in 12 healthy subjects, simultaneous administration of an antacid decreased the area-under-curve (AUC) and maximum concentration (Cmax) of a single dose of itraconazole (200 mg) by 66% and 70%, respectively. Time to Cmax (Tmax) increased by 70%.(15) This interaction has also been reported in a case report.(16) In a study in 3 subjects, simultaneous administration of a combination aluminum hydroxide/magnesium hydroxide (30 ml) decreased the AUC of a single dose of ketoconazole (200 mg) by 41%.(172) In a case report, a patient receiving concurrent ketoconazole with aluminum hydroxide, cimetidine, and sodium bicarbonate did not respond to therapy until cimetidine was discontinued and the administration time of aluminum hydroxide and cimetidine was changed to 2 hours after ketoconazole. In a follow-up study in 2 subjects, concurrent cimetidine and sodium hydroxide lowered ketoconazole levels.(18) In a study in 14 subjects, simultaneous administration of aluminum hydroxide/magnesium hydroxide (20 ml, 1800 mg/1200 mg) had no significant effects on fluconazole pharmacokinetics.(3) In a randomized, open-label, cross-over study in 6 subjects, simultaneous administration of itraconazole with buffered didanosine tablets resulted in undetectable levels of itraconazole.(19) In a randomized cross-over study in 12 HIV-positive subjects, administration of buffered didanosine tablets 2 hours after ketoconazole had no effects on ketoconazole levels.(20) In a randomized, cross-over, open-label study in 24 healthy subjects, simultaneous administration of enteric-coated didanosine had no effect on ketoconazole pharmacokinetics.(21) One or more of the drug pairs linked to this monograph have been included in a list of interactions that could be considered for classification as "non-interruptive" in EHR systems. This DDI subset was vetted by an expert panel commissioned by the U.S. Office of the National Coordinator (ONC) for Health Information Technology.

Antacids; H2 Antagonists/Ledipasvir; Velpatasvir

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)

Antacids; H2 Antagonists/Rilpivirine

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

MECHANISM OF ACTION: Rilpivirine requires an acidic medium for absorption. Antacid or H2 antagonist induced decrease in gastric pH may result in a decrease in rilpivirine absorption.(1)

CLINICAL EFFECTS: Simultaneous administration of an antacid or a H2 antagonist may result in decreased levels and effectiveness of rilpivirine, as well as the development of resistance.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: In patients maintained on rilpivirine, administer antacids at least 2 hours before or 4 hours after rilpivirine.(1) In patients maintained on rilpivirine, administer H2 antagonists at least 12 hours before or 4 hours after rilpivirine.(1) Concurrent use of proton pump inhibitors with rilpivirine is contraindicated.(1) Some vitamin preparations may contain sufficient quantities of calcium and/or magnesium salts with antacid properties to interact as well.

DISCUSSION: In a study in 16 subjects, omeprazole (20 mg daily) decreased the maximum concentration (Cmax), area-under-curve (AUC), and minimum concentration (Cmin) of rilpivirine (150 mg daily) by 40%, 40%, and 33%, respectively. The Cmax and AUC of omeprazole decreased by 14% and 14%, respectively.(1) In a study in 24 subjects, famotidine (40 mg single dose) administered 12 hours before a single dose of rilpivirine (150 mg) had no significant effect on rilpivirine Cmax or AUC.(1) In a study in 23 subjects, famotidine (40 mg single dose) administered 2 hours before a single dose of rilpivirine (150 mg) decreased the rilpivirine Cmax and AUC by 85% and 76%, respectively.(1) In a study in 24 subjects, famotidine (40 mg single dose) administered 4 hours after a single dose of rilpivirine (150 mg) increased the rilpivirine Cmax and AUC by 21% and 13%, respectively.(1)

Antacids; Selected H2 Antagonists/Acalabrutinib Capsules

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

MECHANISM OF ACTION: Acalabrutinib capsules solubility decreases with increasing pH. Antacid or H2 antagonist induced increase in gastric pH may result in a decrease in acalabrutinib capsules absorption.(1)

CLINICAL EFFECTS: Simultaneous administration of an antacid or a H2 antagonist may result in decreased levels and effectiveness of acalabrutinib capsules.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Separate administration of acalabrutinib capsules and antacids by at least 2 hours.(1) In patients on acalabrutinib capsules, administer acalabrutinib capsules at least 2 hours before taking H2 antagonists.(1) Concurrent use of proton pump inhibitors with acalabrutinib capsules is not recommended.(1) Some vitamin preparations may contain sufficient quantities of calcium and/or magnesium salts with antacid properties to interact as well. Acalabrutinib tablets are not affected by coadministration with H2 antagonists or antacids, and may be used concurrently.(1)

DISCUSSION: In a study in healthy subjects, coadministration with an antacid (calcium carbonate 1 gram) decreased area-under-curve (AUC) of acalabrutinib capsules by 53%. Coadministration with a proton pump inhibitor (omeprazole 40 mg for 5 days) decreased AUC of acalabrutinib capsules by 43%.(1)

H2 Antagonists/Atazanavir

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

MECHANISM OF ACTION: H-2 antagonists increase gastric pH. As gastric pH increases, the solubility of atazanavir decreases.(1,2)

CLINICAL EFFECTS: Concurrent use of atazanavir and a H-2 antagonist may result in decreased levels and effectiveness of atazanavir.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The Australian and US manufacturers of atazanavir(1,2) and cobicistat(3,4) state that patients who require H-2 antagonist therapy should receive atazanavir 300 mg daily with ritonavir 100 mg daily or cobicistat 150 mg daily, taken with and/or at least 10 hours after the H-2 antagonist dose. Patients who are also on tenofovir in addition to atazanavir and a H-2 antagonist should receive atazanavir 400 mg daily with ritonavir 100 mg daily or cobicistat 150 mg daily.(2,3,5) The dose of the H-2 antagonist should not exceed the equivalent of famotidine 40 mg twice daily in treatment-naive patients, and 20 mg twice daily in treatment-experienced patients.(2-5) Treatment-experienced pregnant patients in the second or third trimester on concurrent tenofovir disoproxil should have their atazanavir dose increased to 400 mg with ritonavir 100 mg daily. The use of atazanavir with both a H2-antagonist and tenofovir in treatment-experienced pregnant women is not recommended.(2) The Australian manufacturer of atazanavir states that atazanavir without ritonavir is not recommended when co-administered with H-2 antagonists.(1) The US manufacturer of atazanavir states that treatment-naive patients who are unable to tolerate ritonavir or cobicistat should receive atazanavir 400 mg daily with food at least 2 hours before and at least 10 hours after the H-2 antagonist. The H-2 antagonist dose should not exceed the equivalent of a 20 mg single dose of famotidine and the total daily dose should not exceed a 40 mg equivalent dose of famotidine. Treatment-experienced patients should not use unboosted atazanavir with a H-2 antagonist.(2) The US manufacturer of atazanavir states that atazanavir should not be administered without ritonavir in pediatric patients at least 13 years of age who weigh at least 40 kg who are receiving a H2 antagonist. Data are not sufficient to recommend a dose of atazanavir in patients weighing less than 40 kg.(2)

DISCUSSION: In a study in 15 subjects, simultaneous administration of atazanavir (400 mg daily) with famotidine (40 mg twice daily) decreased the atazanavir maximum concentration (Cmax), area-under-curve (AUC), and minimum concentration (Cmin) by 47%, 41%, and 42%, respectively.(2) In a study in 14 subjects, atazanavir (400 mg daily) was administered 2 hours before and 10 hours after famotidine (40 mg twice daily). Atazanavir Cmax increased 8%. Atazanavir AUC and Cmin decreased by 5% and 21%, respectively.(2) In a study in 14 subjects, atazanavir (300 mg daily) and ritonavir (100 mg daily) were administered simultaneously with famotidine (40 mg twice daily). Atazanavir Cmax, AUC, and Cmin decreased by 14%, 18%, and 28%, respectively, compared to the same regimen alone. However, atazanavir Cmax was similar to levels seen with atazanavir 400 mg alone. Atazanavir AUC and Cmin were 1.79-fold and 4.46-fold higher than levels seen with atazanavir 400 mg alone.(2) In a study in 18 subjects, simultaneous administration of famotidine (20 mg twice daily) and atazanavir/ritonavir (300/100 mg daily) decreased the Cmax, AUC, and Cmin of atazanavir by 9%, 10%, and 19%, respectively.(2) In a study in 20 subjects, administration of atazanavir/ritonavir/tenofovir (300/100/300 mg daily) 12 hours after famotidine (40 mg daily) decreased the Cmax, AUC, and Cmin of atazanavir by 11%, 12%, and 23%, respectively.(2) In a study in 18 subjects, administration of atazanavir/ritonavir/tenofovir (300/100/300 mg daily) 12 hours after the evening dose and two hours before the morning dose of famotidine (40 mg twice daily) decreased the Cmax, AUC, and Cmin of atazanavir by 26%, 21%, and 28%, respectively.(2) In a study in 15 subjects, administration of atazanavir/ritonavir (400/100 mg) with famotidine (40 mg twice daily) decreased atazanavir Cmin by 14%. There were no significant effects on atazanavir Cmax or AUC.(2)

H2 Antagonists/Pritelivir

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

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

CLINICAL EFFECTS: Coadministration of H2 receptor antagonists may reduce the bioavailability of pritelivir leading to decreased systemic levels and effectiveness.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Take pritelivir at least 2 hours before or 12 hours after H2 receptor antagonists.(1)

DISCUSSION: The combination of pritelivir with H2 receptor antagonists has not been studied. Pritelivir absorption is pH-dependent. Coadministration of a single oral dose of 100 mg pritelivir (on Day 1) with esomeprazole 40 mg once daily (from day -3 to Day 1; 4 days total) decreased maximum concentration (Cmax) by 76% and area-under-curve (AUC) by 59% compared to pritelivir administered alone.(1)

H2 Antagonists/Ravidasvir

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

MECHANISM OF ACTION: Absorption of ravidasvir may be reduced in patients receiving concomitant treatment with acid reducing agents.(1)

CLINICAL EFFECTS: Administration of H2 antagonists may reduce the bioavailability of ravidasvir, leading to decreased systemic levels and effectiveness.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: In order to assure systemic absorption and maximal effectiveness from use of this Hepatitis C treatment, counsel patients to administer H2 antagonists 4 hours after ravidasvir.(1)

DISCUSSION: Interaction studies with antacids have not been performed. Co-administration with H2 antagonists are expected to decrease ravidasvir plasma concentrations and potentially result in Hepatitis C treatment failure.(1)

H2 Antagonists/Rilzabrutinib

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

MECHANISM OF ACTION: Rilzabrutinib solubility decreases with increasing pH. H2 antagonist induced increase in gastric pH may result in a decrease in rilzabrutinib absorption.(1)

CLINICAL EFFECTS: Simultaneous administration of a H2 antagonist may result in decreased levels and effectiveness of rilzabrutinib.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Administer rilzabrutinib at least 2 hours before taking H2 antagonists.(1) Concurrent use of rilzabrutinib with proton pump inhibitors should be avoided.(1)

DISCUSSION: In an interaction study, administration of famotidine (H2 receptor antagonist) two hours after the evening dose of rilzabrutinib decreased the next morning dose of rilzabrutinib maximum concentration (Cmax) by 35% and area-under-curve (AUC) by 28%.(1)

H2 Antagonists/Selected Kinase Inhibitors

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

MECHANISM OF ACTION: The solubility of dacomitinib,(1) erlotinib,(2) gefitinib,(3) and nilotinib(4) is pH dependent. Changes in gastric pH from H2 antagonists may decrease the absorption of dacomitinib,(1) erlotinib,(2) gefitinib,(3) and nilotinib(4).

CLINICAL EFFECTS: Use of H2 antagonists may result in decreased levels and effectiveness of dacomitinib,(1) erlotinib,(2) gefitinib,(3) and nilotinib(4).

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Consider the use of short-acting antacids in patients taking dacomitinib,(1) erlotinib,(2) gefitinib,(3) and nilotinib(4). If antacids are used, separate the administration times by several hours(1-7) but at least 2 hours for bosutinib,(1) and nilotinib,(4) and 6 hours for gefitinib.(3) If H2 antagonist therapy is required with dacomitinib, dacomitinib must be given once daily 10 hours after the H2 blocker and 6 hours before the next dose of the H2 blocker.(1) If H2 antagonist therapy is required with erlotinib or nilotinib, the kinase inhibitor must be given 10 hours after the H2 blocker and at least 2 hours before the next dose of the H2 blocker.(2-4) If H2 antagonist therapy is required with gefitinib, gefitinib should be given at least 6 hours before or after the H2 antagonist.(3) Avoid the use of proton pump inhibitors (PPIs) in patients receiving treatment dacomitinib,(1) erlotinib,(2) gefitinib,(3) and nilotinib(4).

DISCUSSION: In a study, concurrent rabeprazole decreased the Cmax and AUC of dacomitinib by 51% and 39%, respectively.(1) In a study, concurrent omeprazole decreased the AUC and Cmax of erlotinib by 46% and 61%, respectively.(2) In a study, administration of erlotinib two hours after a dose of ranitidine (300 mg), erlotinib AUC and Cmax decreased by 33% and 54%, respectively. Administration of erlotinib 10 hours after and two hours before ranitidine (150 mg twice daily), erlotinib AUC and Cmax decreased by 15% and 17%, respectively.(2) In a case report, a patient that was given erlotinib (150 mg daily,) with algeldrate/magnesium hydroxide (800/400 mg four times daily 4 hours before or 2 hours after erlotinib) did not see a significant reduction in serum trough concentrations of erlotinib. When the patient was switched to intravenous pantoprazole via continuous infusion (8 mg per hour), serum erlotinib levels decreased significantly below minimal trough concentrations for effective tyrosine kinase inhibition. When the patient was switched to oral pantoprazole (40 mg twice daily), serum trough levels of erlotinib returned to therapeutic levels.(5) In a study in 22 healthy subjects, pretreatment with esomeprazole (40 mg daily), decreased the Cmax and AUC of a single dose of nilotinib (400 mg) by 27% and 34%, respectively.(4,7) Increasing the dosage of nilotinib or separating the administration time of nilotinib and the proton pump inhibitor is not expected to eliminate the interaction.(4) There were no significant changes in nilotinib pharmacokinetics when famotidine was administered 10 hours before or 2 hours after nilotinib.(4) There were no significant changes in nilotinib pharmacokinetics when an antacid (aluminum hydroxide/magnesium hydroxide/simethicone) was administered 2 hours before or after nilotinib.(4)

H2 Antagonists; Proton Pump Inhibitors/Amphetamines

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

MECHANISM OF ACTION: H2 antagonists and proton pump inhibitors (PPIs) may alter the timing of absorption of amphetamines.

CLINICAL EFFECTS: Concurrent use of amphetamines and H2 antagonists or PPIs may result in an increased absorption rate and a change in timing of peak amphetamine levels.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer states that patients receiving concurrent amphetamines and H2 antagonists or PPIs should be monitored for changes in the timing and clinical effects of amphetamines.(1) Monitor patients receiving concurrent therapy for changes in amphetamine effectiveness and side effects. The Canadian manufacturer states that concurrent use of proton pump inhibitors and amphetamines should be avoided.(3)

DISCUSSION: During concurrent use of a proton pump inhibitor, the median time to maximum concentration (Tmax) of Adderall XR decreased from 5 hours to 2.75 hours.(3) In a 4-way crossover study in healthy subjects, omeprazole had no effect on the total exposure a single dose of mixed amphetamine salts (20 mg); however median Tmax decreased from 5 hours to 2.75 hours. Approximately 50% of subjects had a decrease in Tmax of equal to or greater than 1 hour.(4)

Sel Oral Cations; Antacids; H2 Antag/Dolutegravir-Rilpivirin

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

MECHANISM OF ACTION: Aluminum, calcium, iron, lanthanum, magnesium, sucralfate, and zinc may form chelation compounds with dolutegravir.(1) Rilpivirine requires an acidic medium for absorption. Antacid or H2 antagonist induced decrease in gastric pH may result in decrease in rilpivirine absorption.(1)

CLINICAL EFFECTS: Simultaneous administration or administration of products containing aluminum, calcium, iron, lanthanum, magnesium, and/or sucralfate close to the administration time of dolutegravir may result in decreased absorption and clinical effectiveness of dolutegravir.(1) Simultaneous administration of an antacid or a H2 antagonist may result in decreased levels and effectiveness of rilpivirine, as well as the development of resistance.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If possible, avoid concurrent therapy with dolutegravir-rilpivirine and cation-containing products. If it is necessary to use these agents concurrently, dolutegravir-rilpivirine should be administered 4 hours before or 6 hours after taking these medications.(1) Alternatively, dolutegravir-rilpivirine and supplements containing calcium or iron can be taken together with food.(1) In patients maintained on dolutegravir-rilpivirine, administer dolutegravir-rilpivirine at least 4 hours before or 6 hours after antacids .(1) In patients maintained on dolutegravir-rilpivirine, administer dolutegravir-rilpivirine at least 4 hours before or 12 hours after H2 antagonists.(1) Concurrent use of proton pump inhibitors will dolutegravir-rilpivirine is contraindicated.(1)

DISCUSSION: In a study in 16 subjects, the administration of an antacid (Maalox - aluminum and magnesium hydroxide) simultaneously with dolutegravir (50 mg single dose) decreased the maximum concentration (Cmax), area-under-curve (AUC), and minimum concentration (Cmin) of dolutegravir by 72%, 74%, and 74%, respectively.(1) In a study in 16 subjects, the administration of an antacid (Maalox - aluminum and magnesium hydroxide) 2 hours after dolutegravir (50 mg single dose) decreased dolutegravir Cmax, AUC, and Cmin by 18%, 26%, and 30%, respectively.(1) In a study in 16 subjects, the administration of a multiple vitamin (One-A-Day) simultaneously with dolutegravir (50 mg single dose) decreased dolutegravir Cmax, AUC, and Cmin by 35%, 33%, and 32%, respectively.(1) In a study in 16 subjects, omeprazole (20 mg daily) decreased the Cmax, AUC, and Cmin of rilpivirine (150 mg daily) by 40%, 40%, and 33%, respectively. The Cmax and AUC of omeprazole decreased by 14% and 14%, respectively.(1) In a study in 24 subjects, famotidine (40 mg single dose) administered 12 hours before a single dose of rilpivirine (150 mg) had no significant effect on rilpivirine Cmax or AUC.(1) In a study in 23 subjects, famotidine (40 mg single dose) administered 2 hours before a single dose of rilpivirine (150 mg) decreased the rilpivirine Cmax and AUC by 85% and 76%, respectively.(1) In a study in 24 subjects, famotidine (40 mg single dose) administered 4 hours before a single dose of rilpivirine (150 mg) increased the rilpivirine Cmax and AUC by 21% and 13%, respectively.(1)

Selected H2 Antagonists/Bosutinib; Neratinib

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

MECHANISM OF ACTION: The solubility of bosutinib(1) and neratinib(2) is pH dependent. Changes in gastric pH from H2 antagonists may decrease the absorption of bosutinib and neratinib.

CLINICAL EFFECTS: Use of H2 antagonists may result in decreased levels and effectiveness of bosutinib(1) and neratinib.(2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Consider the use of short-acting antacids in patients taking bosutinib(1) and neratinib.(2) If antacids are used, separate the administration times by at least 2 hours for bosutinib(1) and 3 hours for neratinib.(2) If H2 antagonist therapy is required with bosutinib, separate administration of the H2 blocker by at least 2 hours before or 2 hours after bosutinib.(1) If H2 antagonist therapy is required with neratinib, then neratinib must be given 10 hours after the H2 blocker and at least 2 hours before the next dose of the H2 blocker.(2) Avoid the use of proton pump inhibitors (PPIs) in patients receiving treatment with bosutinib(1) and neratinib.(2)

DISCUSSION: A single dose of bosutinib 400 mg was administered alone or following multiple doses of lansoprazole 60 mg without food. Lansoprazole decreased bosutinib maximum concentration (Cmax) and area-under-curve (AUC) by 46% and 26%, respectively.(1) In a study in 15 healthy subjects, lansoprazole 30 mg daily decreased the Cmax and AUC of a single dose of neratinib (240 mg) by 71% and 65%, respectively.(2)

Selected H2 Antagonists/Pexidartinib

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

MECHANISM OF ACTION: The solubility of pexidartinib is pH dependent. Changes in gastric pH from H2 antagonists may decrease the absorption of pexidartinib.(1)

CLINICAL EFFECTS: Use of H2 antagonists may result in decreased levels and effectiveness of pexidartinib.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Consider the use of short-acting antacids in patients taking pexidartinib. If antacids are used, separate the administration times by at least 2 hours. If H2 antagonist therapy is required, the pexidartinib must be given 10 hours after the H2 blocker and at least 2 hours before the next dose of the H2 blocker. Avoid the use of proton pump inhibitors (PPIs).(1)

DISCUSSION: Coadministration of esomeprazole decreased pexidartinib maximum concentration (Cmax) and area-under-curve (AUC) by 55% and 50%, respectively.(1)

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There are no contraindication contraindications for this drug.

• Chronic kidney disease stage 3A (moderate) GFR 45-59 ml/min
• Chronic kidney disease stage 3B (moderate) GFR 30-44 ml/min
• Chronic kidney disease stage 4 (severe) GFR 15-29 ml/min
• Chronic kidney disease stage 5 (failure) GFr<15 ml/min
• Gastric cancer

• Kidney disease with likely reduction in glomerular filtration rate (GFr)

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Rare or Very Rare

• Abnormal hepatic function tests
• Agranulocytosis
• Anaphylaxis
• Anemia
• Angioedema
• Atrioventricular block
• Bronchospastic pulmonary disease
• Cardiac arrhythmia
• Dyspnea
• Hepatitis
• Hypotension
• Increased alanine transaminase
• Increased aspartate transaminase
• Interstitial pneumonitis
• Leukopenia
• Obstructive hyperbilirubinemia
• Pancytopenia
• Psychiatric disorder
• Rhabdomyolysis
• Seizure disorder
• Skin rash
• Stevens-johnson syndrome
• Thrombocytopenic disorder
• Toxic epidermal necrolysis
• Urticaria

More Frequent

• Constipation
• Diarrhea
• Dizziness
• Headache disorder

Less Frequent

• Musculoskeletal pain

Rare or Very Rare

• Acne vulgaris
• Acute abdominal pain
• Acute cognitive impairment
• Agitation
• Allergic conjunctivitis
• Alopecia
• Anorexia
• Anticholinergic toxicity
• Arthralgia
• Cramps
• Delirium
• Drowsy
• Dry skin
• Dysgeusia
• Facial edema
• Fatigue
• Fever
• Flushing
• General weakness
• Hallucinations
• Insomnia
• Lethargy
• Nausea
• Paresthesia
• Pruritus of skin
• Tinnitus
• Vomiting
• Xerostomia

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Reproduction studies in rats and rabbits using oral famotidine dosages up to 2 (approximately 2500 times the maximum human dosage) and 0.5 g/kg daily, respectively, or IV dosages up to 0.2 (approximately 250 times the maximum human dosage) and 0.1 g/kg daily, respectively, have not revealed evidence of harm to the fetus. Oral dosages of 2 g/kg daily inhibited weight gain in pregnant rats, and those of 0.5 and/or 2 g/kg daily on days 7-17 of gestation decreased fetal weight and delayed sternal ossification in the offspring. Decreased food intake and decreased weight gain also occurred in offspring of rats receiving these dosages from days 10-28 post partum. Death and locomotor dysfunction were observed in pregnant rats receiving IV famotidine dosages of 100 or 200 mg/kg daily. IV dosages of 100 or 200 mg/kg daily in rats have decreased pup body weight during the post-weaning period. Although no direct fetotoxic effects have been observed, sporadic abortions and decreases in fetal weight occurred secondary to substantial decreases in food intake in pregnant rabbits receiving oral dosages of 200 mg/kg (250 times the usual human dosage) or more daily. Decreased number of sacrocaudal vertebrae and delayed ossification have occurred in rabbits receiving oral famotidine dosages of 0.5 g/kg daily. There are no adequate and controlled studies to date using famotidine in pregnant women, and the drug should be used during pregnancy only when clearly needed. Women who are pregnant or nursing should seek the advice of a health professional before using famotidine for self-medication.

Famotidine is distributed into milk in humans and in animals. The drug has produced transient growth depression in the offspring of lactating rats receiving dosages at least 600 times the usual human dosage. Because of the potential for serious adverse reactions to famotidine in nursing infants, a decision should be made whether to discontinue nursing or the drug, taking into account the importance of the drug to the woman.

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