Efavirenz 600 mg, Lamivudine 300 mg, Tenofovir Fumarate 300 mg Tablets

Efavirenz, lamivudine and tenofovir disoproxil fumarate tablets are a fixed-dose combination of antiviral drugs EFV, 3TC, and TDF with antiviral activity against HIV-1 [see Microbiology (12.4)].

The effect of food on efavirenz, lamivudine and tenofovir disoproxil fumarate has not been evaluated.

Efavirenz: In HIV-1-infected subjects, time-to-peak plasma concentrations were approximately 3 to 5 hours and steady-state plasma concentrations were reached in 6 to 10 days. EFV is highly bound (approximately 99.5 to 99.75%) to human plasma proteins, predominantly albumin. Following administration of 14C-labeled EFV, 14 to 34% of the dose was recovered in the urine (mostly as metabolites) and 16 to 61% was recovered in feces (mostly as parent drug). In vitro studies suggest CYP3A and CYP2B6 are the major isozymes responsible for EFV metabolism. EFV has been shown to induce CYP enzymes, resulting in induction of its own metabolism. EFV has a terminal half-life of 52 to 76 hours after single doses and 40 to 55 hours after multiple doses.

Lamivudine: After oral administration of 2 mg/kg of 3TC twice a day to 9 adults with HIV-1, the peak serum 3TC concentration (Cmax) was 1.5 ± 0.5 mcg/mL (mean ± SD). The area under the plasma concentration versus time curve (AUC) and Cmax increased in proportion to oral dose over the range from 0.25 to 10 mg/kg and absolute bioavailability in 12 adult patients was 86% ± 16% (mean ± SD) for the 150-mg tablet and 87% ± 13% for the oral solution. Binding of 3TC to human plasma proteins is low (< 36%). Within 12 hours after a single oral dose of 3TC in 6 HIV-l-infected adults, 5.2% ± 1.4% (mean ± SD) of the dose was excreted as the trans-sulfoxide metabolite in the urine. The majority of 3TC is eliminated unchanged in urine by active organic cationic secretion and the observed mean elimination half-life (t1/2) ranged from 5 to 7 hours in most single-dose studies with serum sampling for 24 hours after dosing.

Tenofovir Disoproxil Fumarate: Following oral administration of a single 300 mg dose of TDF to HIV-1-infected subjects in the fasted state, maximum serum concentrations (Cmax) were achieved in 1.0 ± 0.4 hrs (mean ± SD) and Cmax and AUC values were 296 ± 90 ng/mL and 2,287 ± 685 ng•hr/mL, respectively. The oral bioavailability of tenofovir from TDF in fasted subjects is approximately 25%. Less than 0.7% of tenofovir binds to human plasma proteins in vitro and the binding is independent of concentration over the range of 0.01 to 25 mcg/mL. Approximately 70 to 80% of the intravenous dose of tenofovir is recovered as unchanged drug in the urine. Tenofovir is eliminated by a combination of glomerular filtration and active tubular secretion with a renal clearance in adults with normal renal function of 243 ± 33 mL/min (mean ± SD). Following a single oral dose, the terminal elimination half-life of tenofovir is approximately 17 hours.

Race: — Efavirenz and Lamivudine: There are no significant or clinically relevant racial differences in EFV and 3TC pharmacokinetics.

Tenofovir Disoproxil Fumarate: There were insufficient numbers from racial and ethnic groups other than Caucasian to adequately determine potential pharmacokinetic differences among these populations.

Gender: There are no significant or clinically relevant gender differences in the pharmacokinetics of EFV, 3TC, and TDF.

Geriatric Patients: The pharmacokinetics of 3TC and TDF have not been studied in patients over 65 years of age.

Patients with Renal Impairment: [ See Use in Specific Populations (8.6) . ]

Efavirenz: The pharmacokinetics of EFV have not been studied in patients with renal impairment.

Lamivudine:The pharmacokinetics of 3TC are altered in subjects with renal impairment (Table 6).

Tenofovir Disoproxil Fumarate: The pharmacokinetics of TDF are altered in subjects with renal impairment [see Warnings and Precautions (5.4)]. In subjects with creatinine clearance below 50 mL/min or with end-stage renal disease (ESRD) requiring dialysis, Cmax, and AUC0 to ∞ of tenofovir were increased.