Abacavir-Lamivudine (abacavir sulfate/lamivudine)

Abacavir is commercially available as abacavir sulfate; dosage is expressed in terms of abacavir.

Lamivudine is administered orally once or twice daily without regard to meals.

For the treatment of HIV-1 infection, lamivudine is commercially available as an oral solution containing 10 mg/mL or tablets containing 150 or 300 mg of the drug (Epivir(R), generic). The 150-mg scored tablets are the preferred preparation in pediatric patients who weigh 14 kg or more and can swallow tablets. The oral solution should be used in those unable to safely and reliably swallow tablets. Lamivudine is used in conjunction with other antiretrovirals for the treatment of HIV-1 infection.

For the treatment of chronic HBV infection, lamivudine is commercially available as an oral solution containing 5 mg/mL or film-coated tablets containing 100 mg of the drug (Epivir-HBV(R), generic). The 5-mg/mL oral solution should be used in patients requiring a dosage less than 100 mg and in children unable to reliably swallow tablets.

Lamivudine preparations labeled by FDA for treatment of chronic HBV infection should not be used in HIV-infected patients because they contain a lower dosage of the drug than that required for treatment of HIV-1 infection. If such preparations are used for the management of chronic HBV infection in a patient with unrecognized or untreated HIV infection, rapid emergence of HIV resistance is likely to result because of the subtherapeutic dose and the inappropriateness of monotherapy for HIV-infected individuals.

Store lamivudine 100-mg, 150-mg, and 300-mg tablets at 25degreesC (excursions permitted between 15-30degreesC). Store lamivudine 5-mg/mL oral solution at 20-25degreesC and store lamivudine 10-mg/mL oral solution at 25degreesC.

Abacavir sulfate is administered orally once or twice daily without regard to meals. If a dose of abacavir is missed, administer the dose as soon as possible. Do not double the next dose or take more than the prescribed dose.

Abacavir is commercially available as a single entity preparation and in the following fixed-combination tablets for oral use: abacavir and lamivudine (Epzicom(R)); abacavir, lamivudine, and zidovudine (Trizivir(R)); and abacavir, dolutegravir, and lamivudine (Triumeq(R) and Triumeq PD(R)). Since the antiretroviral agents contained in the fixed combination preparations also may be available in single-entity or other fixed-combination preparations, exercise care to ensure that therapy is not duplicated if a fixed combination is used in conjunction with other antiretrovirals.

Single-entity abacavir sulfate is commercially available as an oral solution or tablets.

Abacavir oral solution is used in pediatric patients or when a solid oral dosage form is inappropriate.

The scored 300-mg abacavir tablets are used in adults and may be used in children weighing 14 kg or greater who have undergone assessment demonstrating ability to reliably swallow tablets.

Store abacavir tablets and oral solution between 20-25degreesC. The oral solution may also be refrigerated.

The following drug interactions are based on studies using lamivudine. Additional drug interactions may exist for fixed-dose combination products containing lamivudine/zidovudine (Combivir(R), generic) , abacavir/lamivudine (Epzicom(R), generic) , abacavir/lamivudine/zidovudine (Trizivir(R), generic) , lamivudine/tenofovir disoproxil fumarate (Cimduo(R)) , doravirine/lamivudine/tenofovir disoproxil fumarate (Delstrigo(R)) , dolutegravir/lamivudine (Dovato(R)) , efavirenz/lamivudine/tenofovir disoproxil fumarate (Symfi(R); Symfi(R) Lo) , and abacavir/dolutegravir/lamivudine (Triumeq(R); Triumeq PD(R)). See the full prescribing information for information on each of these combination products.

In vitro studies indicate that abacavir has the potential to inhibit cytochrome P-450 (CYP) isoenzyme 1A1, and has limited potential to inhibit CYP3A4. Abacavir does not induce nor inhibit CYP2C9 or CYP2D6. At therapeutic exposures, abacavir is not expected to affect substrates of organic anion transporter polypeptide (OATP)1B1 or OATP1B3, breast cancer resistance protein (BCRP), P-glycoprotein (P-gp), organic cation transporter (OCT)1, OCT2, or multidrug and toxic extrusion protein (MATE)1 and MATE2-K.

In vitro studies indicate that abacavir is a substrate of BCRP and P-gp; however, the concomitant use of modulators of these transporters is not expected to have clinically relevant effects on abacavir serum concentrations. In vitro studies indicate that abacavir is not a substrate of OATP1B1, OAP1B3, OCT1, OCT2, OAT1, MATE1, MATE2-K, or multidrug resistance-associated protein (MRP)2, or MRP4; therefore, the concomitant use of agents that modulate these transporters is not expected to affect abacavir serum concentrations.

The following drug interactions are based on studies using abacavir. Additional drug interactions may exist for fixed-dose combinations containing abacavir and lamivudine (Epzicom(R)); abacavir, lamivudine, and zidovudine (Trizivir(R)); and abacavir, dolutegravir, and lamivudine (Triumeq(R) and Triumeq PD(R)). See the full prescribing information for drug interactions of each of these combination products.

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

Anti-Retrovirals/Atidarsagene Autotemcel

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: Atidarsagene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating lentiviral vector. Antiretrovirals may interfere with the manufacturing of apheresed cells.

CLINICAL EFFECTS: Use of antiretrovirals before mobilization and apheresis may interfere with the production of atidarsagene autotemcel.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discontinue antiretrovirals for at least one month prior to mobilization (or the expected duration of time needed for elimination of the medication) until all cycles of apheresis are completed. If a patient requires antiretrovirals for HIV prophylaxis, then confirm a negative HIV test before beginning mobilization and apheresis of CD34+ cells.

DISCUSSION: Antiretroviral medications may interfere with the manufacturing of atidarsagene autotemcel therapy.(1)

Anti-Retrovirals/Elivaldogene Autotemcel

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: Elivaldogene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating lentiviral vector. Antiretrovirals may interfere with the manufacturing of apheresed cells.

CLINICAL EFFECTS: Use of antiretrovirals before mobilization and apheresis may interfere with the production of elivaldogene autotemcel.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discontinue antiretrovirals for at least one month prior to mobilization and until all cycles of apheresis are completed. If a patient requires antiretrovirals for HIV prophylaxis, then confirm a negative HIV test before beginning mobilization and apheresis of CD34+ cells.

DISCUSSION: Antiretroviral medications may interfere with the manufacturing of elivaldogene autotemcel therapy.(1)

Anti-Retrovirals/Etuvetidigene Autotemcel

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: Etuvetidigene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating HIV-based lentiviral vector. Antiretrovirals may interfere with the manufacturing of the apheresed cells.

CLINICAL EFFECTS: Use of antiretrovirals before mobilization and apheresis may interfere with the production of etuvetidigene autotemcel.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients should not take antiretrovirals for at least one month prior to mobilization and until at least 7 days after etuvetidigene autotemcel infusion.(1) If a patient requires antiretroviral agents for HIV post-exposure prophylaxis, etuvetidigene autotemcel treatment should be delayed until HIV testing is negative at 6 months post-exposure.(1)

DISCUSSION: Antiretroviral medications may interfere with the manufacturing of etuvetidigene autotemcel therapy.(1)

Anti-Retrovirals/Lovotibeglogene Autotemcel

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: Lovotibeglogene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating lentiviral vector. Antiretrovirals may interfere with the manufacturing of apheresed cells.

CLINICAL EFFECTS: Use of antiretrovirals before mobilization and apheresis may interfere with the production of lovotibeglogene autotemcel.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discontinue antiretrovirals for at least one month prior to mobilization and until all cycles of apheresis are completed.(1) There are some long-acting antiretroviral medications that may require a longer duration of discontinuation for elimination of the medication. If a patient is taking anti-retrovirals for HIV prophylaxis, confirm a negative test for HIV before beginning mobilization and apheresis of CD34+ cells.(1)

DISCUSSION: Antiretroviral medications may interfere with the manufacturing of lovotibeglogene autotemcel therapy.(1)

Anti-Retrovirals; Hydroxyurea/Betibeglogene Autotemcel

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: Betibeglogene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating lentiviral vector. Antiretrovirals may interfere with the manufacturing of apheresed cells. Hydroxyurea may interfere with hematopoietic stem cell (HSC) mobilization of CD34+ cells.(1)

CLINICAL EFFECTS: Use of hydroxyurea before mobilization may result in unsuccessful stem cell mobilization. Use of antiretrovirals before mobilization and apheresis may interfere with the production of betibeglogene autotemcel.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discontinue antiretrovirals and hydroxyurea for at least one month prior to mobilization and until all cycles of apheresis are completed. If a patient requires antiretrovirals for HIV prophylaxis, then confirm a negative HIV test before beginning mobilization and apheresis of CD34+ cells.

DISCUSSION: Antiretroviral medications and hydroxyurea may interfere with the manufacturing of betibeglogene autotemcel therapy.(1)

Emtricitabine; Lamivudine/Islatravir

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: Emtricitabine and lamivudine may inhibit the intracellular phosphorylation of islatravir by deoxycytidine kinase (dCK).(1)

CLINICAL EFFECTS: Concurrent administration of emtricitabine or lamivudine with islatravir may result in decreased clinical efficacy of islatravir.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of the doravirine-islatravir fixed-dose combination states that co-administration with emtricitabine or lamivudine is contraindicated.(1)

DISCUSSION: Islatravir undergoes a series of phosphorylations to its active metabolites.(1) In a clinical study in healthy participants, co-administration of multiple daily doses of 300 mg lamivudine and a single dose of 2 mg islatravir (8 times the recommended dosage) decreased intracellular ISL-TP (islatravir active metabolite) area under the curve (AUC) level by 87% and maximum concentration (Cmax) by 76% relative to islatravir alone. A similar effect is anticipated when islatravir is co-administered with emtricitabine.(1,2) Compounds phosphorylated by dCK and linked to this monograph include: emtricitabine and lamivudine.

Lamivudine/Zalcitabine

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: Lamivudine and zalcitabine may inhibit the intracellular phosphorylation of each other.(1-6)

CLINICAL EFFECTS: Concurrent administration of lamivudine and zalcitabine may result in decreased clinical efficacy of one or both agents.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of lamivudine states that the concurrent use of lamivudine and zalcitabine is not recommended.(1-3)

DISCUSSION: Both lamivudine(1-3) and zalcitabine(7) undergo a series of phosphorylations to their active metabolites. In an in vitro study, the presence of lamivudine significantly decreased the phosphorylation of zalcitabine, resulting in a 50% decrease in zalcitabine triphosphate levels.(4) In an in vitro study in peripheral blood mononuclear cells (PBMCs) and U937 cells, zalcitabine significantly inhibited the phosphorylation of lamivudine. No lamivudine triphosphate was found in the PBMCs and the amount of lamivudine triphosphate was decreased 33% when compared to control values in the U937 cell line.(5) In another in vitro study, lamivudine decreased total zalcitabine phosphates by 57%. There was no effect on lamivudine phosphorylation.(6)

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

Abacavir/Riociguat

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

MECHANISM OF ACTION: Riociguat is primarily metabolized by CYP1A1 and to a lesser extent by CYP3A4/3A5 and CYP2J2.(1,2) Abacavir has been shown to inhibit CYP1A1 in vitro and may decrease the metabolism of riociguat.(2,3)

CLINICAL EFFECTS: Concurrent use of abacavir with riociguat may result in elevated systemic levels and toxicity (e.g. hypotension) from riociguat.(2,3)

PREDISPOSING FACTORS: The risk for riociguat-associated hypotension is higher in patients with a systolic blood pressure (SBP) < or = 110 prior to treatment initiation or dose increase. Patient specific factors such as renal or hepatic impairment, or age > 65 years are associated with higher systemic exposure to riociguat and may increase interaction risk or severity.(1,4)

PATIENT MANAGEMENT: The US manufacturer of abacavir states that the dose of riociguat may need to be reduced when used concurrently.(3) Although the manufacturer of riociguat does not make any recommendations for dose adjustment when used with a CYP1A1 inhibitor, it has been suggested that the initial dose of riociguat be reduced to 0.5 mg 3 times daily. This is the same dose modification recommended during concurrent therapy with strong CYP and P-gp/BCRP inhibitors, based on a similar magnitude of interaction between riociguat and ketoconazole.(2) Monitor blood pressure and counsel patient to report low blood pressure, lightheadedness or chest pain. Patients stabilized on concomitant therapy may need to have their riociguat dose retitrated upward after discontinuation of abacavir.

DISCUSSION: In an interaction study of 8 HIV-positive patients without pulmonary hypertension, abacavir (given as a fixed-dose combination of abacavir 600 mg-dolutegravir 50 mg-lamivudine 300 mg once daily) increased the area-under-curve (AUC) of single-dose riociguat 0.5 mg by about 3-fold, compared to historical healthy volunteers administered single-dose riociguat 0.5 mg alone.(2) The frequency or magnitude of this interaction is difficult to predict in a specific patient due to significant interpatient variability in drug kinetics. For example, between patient variability in systemic exposure (AUC) relative to dose is 90%. The amount of riociguat metabolized may be as low as 27% or as high as 72%. Cigarette smoking induces the CYP1A1 mediated metabolism of riociguat leading to about a 50% decrease in systemic exposure compared with non-smoking patients.

Anti-Retrovirals/Marnetegragene Autotemcel

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

MECHANISM OF ACTION: Marnetegragene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating lentiviral vector. Antiretrovirals may interfere with the manufacturing of transduced cells.

CLINICAL EFFECTS: Use of antiretrovirals before mobilization and apheresis may interfere with the production of marnetegragene autotemcel.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discontinue antiretrovirals for at least one month prior to mobilization (or the expected duration of time needed for elimination of the antiretrovirals) until all cycles of apheresis are completed. If a patient requires antiretrovirals for HIV prophylaxis, then confirm a negative HIV test before beginning mobilization and apheresis of CD34+ cells.(1)

DISCUSSION: Antiretroviral medications may interfere with the manufacturing of marnetegragene autotemcel.(1)

Deoxycytidine Kinase Substrates/Cladribine Oral

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

MECHANISM OF ACTION: Clofarabine, cytarabine, emtricitabine, fludarabine, gemcitabine, lamivudine, molnupiravir, nelarabine and zalcitabine may inhibit the intracellular phosphorylation of cladribine by deoxycytidine kinase (dCK).

CLINICAL EFFECTS: Concurrent administration of clofarabine, cytarabine, emtricitabine, fludarabine, gemcitabine, lamivudine, molnupiravir, nelarabine, or zalcitabine with cladribine may result in decreased clinical efficacy of cladribine.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of lamivudine states that the concurrent use of lamivudine and cladribine is not recommended.(1) The manufacturer of cladribine states that concurrent use of compounds that require activation by intracellular phosphorylation should be avoided.(2)

DISCUSSION: Cladribine undergoes a series of phosphorylations to its active metabolites. In a case report, a patient on lamivudine who received cladribine concurrently did not experience a decrease in his lymphocyte count. After discontinuation of lamivudine and readministration of cladribine, his lymphocytes dropped as expected.(3) It is expected that other compounds phosphorylated by dCK would also decrease cladribine's efficacy.(4) Compounds phosphorylated by dCK include: clofarabine, cytarabine, emtricitabine, fludarabine, gemcitabine, lamivudine, molnupiravir, nelarabine and zalcitabine.

Lamivudine/Sorbitol

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

MECHANISM OF ACTION: Sorbitol increases the osmotic pressure in the intestine, resulting in accelerated small intestinal transit time and decreased absorption and bioavailability of lamivudine.

CLINICAL EFFECTS: Concurrent administration of sorbitol and lamivudine may result in decreased clinical efficacy of lamivudine.(1) Reduction in lamivudine exposure is sorbitol dose-dependent.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of lamivudine states that the concurrent use of lamivudine and sorbitol should be avoided.(1) Consider more frequent monitoring of HBV viral load when chronic coadministration cannot be avoided.

DISCUSSION: In an open label, randomized sequence, 4-period, crossover trial in 16 healthy adults, coadministration of a single dose of lamivudine (300 mg) with sorbitol (3.2 grams) resulted in a dose-dependent decrease of lamivudine's area-under-the-curve (AUC(0-24), AUC infinity) and maximum concentration (Cmax) of 20%, 28%, and 28%. A single dose of lamivudine with sorbitol (10.2 grams) resulted in a decrease of lamivudine's AUC and Cmax of 39%, 52%, and 52%. A single dose of lamivudine with sorbitol (13.4 grams) resulted in a decrease of lamivudine's AUC and Cmax of 36%, 55%, and 55%.(1)

There are no moderate interactions for this drug.

*Previous hypersensitivity to lamivudine.

*Presence of the human leukocyte antigen (HLA)-B*5701 allele.

*Moderate or severe hepatic impairment.

*History of hypersensitivity reaction to abacavir.

• Acute pancreatitis
• Chronic pancreatitis
• HLa-B *57:01 positive
• Lactation
• Lactic acidosis
• Pancreatitis

• Child-pugh class A hepatic impairment
• 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
• Disease of liver

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

In the treatment of HIV infection in adults, the most common reported adverse reactions (incidence >=15%) were headache, nausea, malaise and fatigue, nasal signs and symptoms, diarrhea, and cough. In the treatment of HIV infection in pediatric patients, the most common reported adverse reactions (incidence >=15%) were fever and cough.

In the treatment of HBV infection, the most common reported adverse reactions (incidence >=10% and reported at a rate greater than placebo) were ear, nose, and throat infections; sore throat; and diarrhea.

Adverse effects of at least moderate intensity reported in 10% or more of adult patients receiving abacavir for HIV-1 infection include nausea, headache, fatigue and malaise, nausea and vomiting, and dreams/sleep disorders.

Adverse effects of at least moderate intensity reported in 5% or more of pediatric patients receiving abacavir for HIV-1 infection include fever and/or chills, nausea and vomiting, skin rash, and ear, nose, and throat infections.

More Frequent

• Hypersensitivity drug reaction

Less Frequent

• Cough
• Pharyngitis

Rare or Very Rare

• Acute myocardial infarction
• Anaphylaxis
• Anemia
• Aplastic anemia
• Erythema multiforme
• Increased alanine transaminase
• Increased aspartate transaminase
• Increased creatine kinase level
• Lactic acidosis
• Lymphadenopathy
• Neutropenic disorder
• Pancreatitis
• Peripheral neuropathy
• Pure red cell aplasia
• Rhabdomyolysis
• Seizure disorder
• Splenomegaly
• Steatosis of liver
• Stevens-johnson syndrome
• Thrombocytopenic disorder
• Toxic epidermal necrolysis
• Urticaria

More Frequent

• Depression
• Diarrhea
• Dizziness
• Fatigue
• Gastritis
• Headache disorder
• Insomnia
• Malaise
• Migraine
• Nausea
• Skin rash
• Symptoms of anxiety
• Vertigo

Less Frequent

• Acute abdominal pain
• Dream disorder
• Fever
• Vomiting

Rare or Very Rare

• Alopecia
• Anorexia
• Arthralgia
• Dyspnea
• Elevated serum amylase
• General weakness
• Hepatitis
• Hyperglycemia
• Hypertriglyceridemia
• Kidney disease with reduction in glomerular filtration rate (GFr)
• Muscle weakness
• Paresthesia
• Pruritus of skin
• Stomatitis
• Weight gain
• Wheezing

No enhanced messaging available.

The safety and efficacy of lamivudine for the treatment of HIV-1 (Epivir(R)) have been established in pediatric patients 3 months of age and older. The scored tablet is the preferred formulation for HIV-1-infected pediatric patients weighing at least 14 kg for whom a solid dosage form is appropriate; in the ARROW trial, pediatric patients who received the oral solution had lower rates of virologic suppression, lower plasma lamivudine exposure, and developed viral resistance more frequently.

The safety and efficacy of lamivudine for the treatment of chronic HBV (Epivir-HBV(R)) in pediatric patients younger than 2 years of age have not been established.

Safety and efficacy of single-entity abacavir tablets or oral solution have been established in infants and children 3 months of age and older. Use of abacavir in children 3 months of age and older is supported by pharmacokinetic trials and evidence from adequate and well-controlled trials in adult and pediatric patients. Safety and efficacy have not been established in neonates and infants less than 3 months of age.

Lamivudine crosses the placenta and is distributed into cord blood in concentrations similar to maternal serum concentrations.

To monitor maternal-fetal outcomes of pregnant women exposed to antiretroviral agents, including lamivudine, the Antiretroviral Pregnancy Registry was established. Clinicians are encouraged to contact the registry at 800-258-4263 or https://www.apregistry.com/ to report cases of prenatal exposure to antiretroviral agents.

Data from the Antiretroviral Pregnancy Registry show no difference in the risk of overall major birth defects for lamivudine compared with the background rate for major birth defects in the US reference population of the Metropolitan Atlanta Congenital Defects Program (MACDP). Reproduction studies in rats or rabbits using oral lamivudine dosages that resulted in plasma concentrations up to approximately 35 times higher than plasma concentrations attained with the recommended human dosage used for the treatment of HIV infection in adults have not revealed evidence of teratogenicity. Although there was evidence of early embryolethality in rabbits at exposure levels similar to those observed in humans, this effect was not seen in rats at exposure levels up to 35 times higher than those in humans.

To monitor maternal-fetal outcomes of pregnant women exposed to antiretroviral agents, including abacavir, the Antiretroviral Pregnancy Registry (APR) was established. Clinicians are encouraged to contact the registry at 800-258-4263 to report cases of prenatal exposure to antiretroviral drugs.

Based on prospective reports to the APR of exposures to abacavir during pregnancy resulting in live births (including over 1,300 exposed in the first trimester and over 1,300 exposed in the second/third trimester), there was no difference between the overall risk of birth defects for abacavir compared with the background birth defect rate of 2.7% in the U.S. reference population of the Metropolitan Atlanta Congenital Defects Program (MACDP). Use of the MACDP population as the comparator group has several limitations; the MACDP assesses populations from a limited geographic area and does not include outcomes for births that occurred at <20 weeks' gestation. The rate of miscarriage is not reported in the APR.

Abacavir crosses the placenta and is distributed into cord blood in concentrations similar to maternal serum concentrations. Concentrations in neonatal plasma at birth were essentially equal to those in maternal plasma at delivery. In animal reproductive studies, abacavir administration during organogenesis resulted in developmental toxicities (i.e., depressed fetal body weight, reduced crown-rump length) and fetal malformations (i.e., fetal anasarca, skeletal malformations) based on abacavir exposure 35 times the usual human exposure (based on AUC). No developmental effects were observed at exposures 3.5-times the usual human exposure (based on AUC).

Lamivudine is distributed into milk in humans. It is not known whether the drug affects human milk production or affects the breast-fed infant.

The HHS perinatal HIV transmission guideline provides updated recommendations on infant feeding. The guideline states that patients with HIV should receive evidence-based, patient-centered counseling to support shared decision making about infant feeding. During counseling, patients should be informed that feeding with appropriate formula or pasteurized donor human milk from a milk bank eliminates the risk of postnatal HIV transmission to the infant. Additionally, achieving and maintaining viral suppression with antiretroviral therapy during pregnancy and postpartum reduces the risk of breastfeeding HIV transmission to <1%, but does not completely eliminate the risk. Replacement feeding with formula or banked pasteurized donor milk is recommended when patients with HIV are not on antiretroviral therapy and/or do not have a suppressed viral load during pregnancy (at a minimum throughout the third trimester), as well as at delivery.

If lamivudine is being used for treatment of chronic HBV infection, the benefits of breast-feeding and the importance of lamivudine to the woman should be considered along with the potential adverse effects on the breast-fed infant from the drug or from the underlying maternal condition.

Abacavir is distributed into human milk. The effects of abacavir on the breastfed infant, or the effects of the drug on milk production are not known.

The HHS perinatal HIV transmission guideline provides updated recommendations on infant feeding. The guideline states that patients with HIV should receive evidence-based, patient-centered counseling to support shared decision making about infant feeding. During counseling, patients should be informed that feeding with appropriate formula or pasteurized donor human milk from a milk bank eliminates the risk of postnatal HIV transmission to the infant. Additionally, achieving and maintaining viral suppression with antiretroviral therapy during pregnancy and postpartum reduces the risk of breastfeeding HIV transmission to <1%, but does not completely eliminate the risk. Replacement feeding with formula or banked pasteurized donor milk is recommended when patients with HIV are not on antiretroviral therapy and/or do not have a suppressed viral load during pregnancy (at a minimum throughout the third trimester), as well as at delivery.

Use with caution in geriatric patients because of age-related decreases in hepatic, renal, and/or cardiac function and concomitant disease and drug therapy.

The manufacturer makes no specific dosage recommendations for single-entity abacavir in geriatric patients. Select dosage with caution due to age-related decreases in hepatic, renal, and/or cardiac function and concomitant disease and drug therapy.

Clinical trials of lamivudine (Epivir(R) and Epivir-HBV(R)) did not include sufficient numbers of patients 65 years of age or older to determine whether they respond differently from younger subjects. Use caution when administering lamivudine to geriatric patients, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

While clinical experience to date has not revealed age-related differences in response to abacavir, clinical studies evaluating abacavir have not included sufficient numbers of adults 65 years of age or older to determine whether geriatric patients respond differently than younger adults. Dosage of abacavir for geriatric patients should be selected carefully because of limited experience with the drug in this age group and because these individuals frequently have decreased hepatic, renal, and/or cardiac function and concomitant disease and drug therapy.