Abacavir (ABC) and Efavirenz (EFV) Pharmacokinetics (PK) in Adefovir (ADV)-Containing Salvage Regimens

G. MORSE*, K. SQUIRES, S. HAMMER, M. FISCHL, V. DEGRUTTOLA, and the ACTG 372 and 368 Protocal Teams. Adult ACTG, NIAID, Bethesda, MD

ACTG 372B is a salvage protocol for patients with virologic failure on zidovudine, lamivudine and indinavir who were randomized to EFV 600 mg qd, ADV 120 mg qd, +/- nelfinavir 750 mg q8h, and ABC 300 mg q12h or 1-2 NRTIs.  Patients receiving nelfinavir were excluded to avoid the influence of nelfinavir on EFV pk.  Patients in ACTG 368 were zidovudine and lamivudine experienced and then received EFV and indinavir +/- ABC.  The pk of these agents were determined after 2 weeks.  The ADV dose was later lowered to 60 mg qd as a result of renal toxicity.  Pk (+ sd) results for area under the concentration-time curve (AUC), total clearance (CI) and half-life (t 1/2) were:

Conclusions: These data indicate that ABC pk in ADV-containing regimens were similar to indinavir/ABC regimens and to prior ABC pk data (mean C1: 10.3 L/hr).  ADV pk were similar to prior data for non-ABC or non-EFV regimens.

Key Words: abacavir, adefovir, efavirenz

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