Abacavir and Lamivudine (Page 5 of 7)

Effect of Food on Absorption of Abacavir and Lamivudine Tablets

Abacavir and lamivudine tablets may be administered with or without food. Administration with a high-fat meal in a single-dose bioavailability trial resulted in no change in AUC last , AUC , and C max for lamivudine. Food did not alter the extent of systemic exposure to abacavir (AUC ), but the rate of absorption (C max ) was decreased approximately 24% compared with fasted conditions (n = 25). These results are similar to those from previous trials of the effect of food on abacavir and lamivudine tablets administered separately.

Specific Populations

Patients with Renal Impairment:

Abacavir and Lamivudine Tablets

The effect of renal impairment on the combination of abacavir and lamivudine has not been evaluated (see the U.S. prescribing information for the individual abacavir and lamivudine components).

Patients with Hepatic Impairment:

Abacavir and Lamivudine Tablets:

The effect of hepatic impairment on the combination of abacavir and lamivudine has not been evaluated (see the U.S. prescribing information for the individual abacavir and lamivudine components).

Pregnant Women:

Abacavir:

Abacavir pharmacokinetics were studied in 25 pregnant women during the last trimester of pregnancy receiving abacavir 300 mg twice daily. Abacavir exposure (AUC) during pregnancy was similar to those in postpartum and in HIV-infected non-pregnant historical controls. Consistent with passive diffusion of abacavir across the placenta, abacavir concentrations in neonatal plasma cord samples at birth were essentially equal to those in maternal plasma at delivery.

Lamivudine :

Lamivudine pharmacokinetics were studied in 36 pregnant women during 2 clinical trials conducted in South Africa. Lamivudine pharmacokinetics in pregnant women were similar to those seen in non-pregnant adults and in postpartum women. Lamivudine concentrations were generally similar in maternal, neonatal, and umbilical cord serum samples.

Pediatric Patients:

Abacavir and lamivudine

The pharmacokinetic data for abacavir and lamivudine following administration of abacavir and lamivudine tablets in pediatric subjects weighing 25 kg and above are limited. The dosing recommendations in this population are based on the safety and efficacy established in a controlled trial conducted using either the combination of EPIVIR and ZIAGEN or abacavir and lamivudine tablets. Refer to the EPIVIR and ZIAGEN USPI for pharmacokinetic information on the individual products in pediatric patients [see DOSAGE AND ADMINISTRATION ( 2.3), ADVERSE REACTIONS ( 6.2), CLINICAL STUDIES ( 14.2)] .

Geriatric Patients:

The pharmacokinetics of abacavir and lamivudine have not been studied in subjects over 65 years of age.

Male and Female Patients:

There are no significant or clinically relevant gender differences in the pharmacokinetics of the individual components (abacavir or lamivudine) based on the available information that was analyzed for each of the individual components.

Racial Groups:

There are no significant or clinically relevant racial differences in pharmacokinetics of the individual components (abacavir or lamivudine) based on the available information that was analyzed for each of the individual components.

Drug Interaction Studies:

The drug interactions described are based on trials conducted with abacavir or lamivudine as single entities; no drug interaction trials have been conducted with abacavir and lamivudine tablets.

Effect of Abacavir and Lamivudine on the Pharmacokinetics of Other Agents:

Abacavir and lamivudine do not inhibit or induce CYP enzymes (such as CYP3A4, CYP2C9, or CYP2D6); therefore, it is unlikely that clinically significant drug interactions will occur with drugs metabolized through these pathways. Based on in vitro study results, abacavir and lamivudine at therapeutic drug exposures are not expected to affect the pharmacokinetics of drugs that are substrates of the following transporters: organic anion transporter polypeptide (OATP)1B1/3, breast cancer resistance protein (BCRP) or P-glycoprotein (P-gp), organic cation transporter (OCT)1, OCT2, OCT3 (lamivudine only), or multidrug and toxic extrusion protein (MATE)1 and MATE2-K.

Effect of Other Agents on the Pharmacokinetics of Abacavir or Lamivudine:

Abacavir and lamivudine are not significantly metabolized by cytochrome P450 enzymes; therefore, CYP enzyme inhibitors or inducers are not expected to affect their concentrations. In vitro, abacavir is not a substrate of OATP1B1, OATP1B3, OCT1, OCT2, OAT1, MATE1, MATE2-K, multidrug resistance-associated protein 2 (MRP2) or MRP4; therefore, drugs that modulate these transporters are not expected to affect abacavir plasma concentrations. Abacavir is a substrate of BCRP and P-gp in vitro; however, considering its absolute bioavailability (83%), modulators of these transporters are unlikely to result in a clinically relevant impact on abacavir concentrations.

Lamivudine is a substrate of MATE1, MATE2-K, and OCT2 in vitro. Trimethoprim (an inhibitor of these drug transporters) has been shown to increase lamivudine plasma concentrations. This interaction is not considered clinically significant as no dose adjustment of lamivudine is needed.

Lamivudine is a substrate of P-gp and BCRP; however, considering its absolute bioavailability (87%), it is unlikely that these transporters play a significant role in the absorption of lamivudine. Therefore, coadministration of drugs that are inhibitors of these efflux transporters is unlikely to affect the disposition and elimination of lamivudine.

Abacavir: Lamivudine and/or Zidovudine

Fifteen HIV-1-infected subjects were enrolled in a crossover-designed drug interaction trial evaluating single doses of abacavir (600 mg), lamivudine (150 mg), and zidovudine (300 mg) alone or in combination. Analysis showed no clinically relevant changes in the pharmacokinetics of abacavir with the addition of lamivudine or zidovudine or the combination of lamivudine and zidovudine. Lamivudine exposure (AUC decreased 15%) and zidovudine exposure (AUC increased 10%) did not show clinically relevant changes with concurrent abacavir.

Lamivudine: Zidovudine

No clinically significant alterations in lamivudine or zidovudine pharmacokinetics were observed in 12 asymptomatic HIV-1-infected adult subjects given a single dose of zidovudine (200 mg) in combination with multiple doses of lamivudine (300 mg every 12 h).

Other Interactions

Ethanol

Abacavir has no effect on the pharmacokinetic properties of ethanol. Ethanol decreases the elimination of abacavir causing an increase in overall exposure.

Interferon Alfa

There was no significant pharmacokinetic interaction between lamivudine and interferon alfa in a trial of 19 healthy male subjects.

Methadone

In a trial of 11 HIV-1-infected subjects receiving methadone-maintenance therapy (40 mg and 90 mg daily), with 600 mg of ZIAGEN twice daily (twice the currently recommended dose), oral methadone clearance increased 22% (90% CI: 6% to 42%) [see DRUG INTERACTIONS ( 7)]. The addition of methadone has no clinically significant effect on the pharmacokinetic properties of abacavir.

Ribavirin

In vitro data indicate ribavirin reduces phosphorylation of lamivudine, stavudine, and zidovudine. However, no pharmacokinetic (e.g., plasma concentrations or intracellular triphosphorylated active metabolite concentrations) or pharmacodynamic (e.g., loss of HIV-1/HCV virologic suppression) interaction was observed when ribavirin and lamivudine (n = 18), stavudine (n = 10), or zidovudine (n = 6) were coadministered as part of a multi-drug regimen to HIV-1/HCV co-infected subjects [see WARNINGS AND PRECAUTIONS ( 5.4)] .

Sorbitol (Excipient)

Lamivudine and sorbitol solutions were coadministered to 16 healthy adult subjects in an open-label, randomized-sequence, 4-period, crossover trial. Each subject received a single 300-mg dose of lamivudine oral solution alone or coadministered with a single dose of 3.2 grams, 10.2 grams, or 13.4 grams of sorbitol in solution. Coadministration of lamivudine with sorbitol resulted in dose-dependent decreases of 20%, 39%, and 44% in the AUC (0-24) ; 14%, 32%, and 36% in the AUC (∞) ; and 28%, 52%, and 55% in the C max ; of lamivudine, respectively.

The effects of other coadministered drugs on abacavir or lamivudine are provided in Table 3.

Table 3. Effect of Coadministered Drugs on Abacavir or Lamivudine

↑ = Increase; ↔ = No significant change; AUC = Area under the concentration versus time curve; CI = Confidence interval.

*
The drug-drug interaction was only evaluated in males
Coadministered Drug Drug and n Concentrations of Abacavir or Lamivudine Concentration of
and Dose Dose AUC Variability Coadministered Drug
Ethanol 0.7 g/kg Abacavir Single 600 mg 24 ↑41% 90% CI: 35% to 48% *
Nelfinavir 750 mg every 8 h x 7 to 10 days Lamivudine Single 150 mg 11 ↑10% 95% CI: 1% to 20%
Trimethoprim 160 mg/ Sulfamethoxazole 800 mg daily x 5 days Lamivudine Single 300 mg 14 ↑43% 90% CI: 32% to 55%

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