Drug Interactions of Amprenavir and Efavirenz, in Combination With a Second Protease Inhibitor, in HIV-Negative Volunteers

The purpose of this study is to measure the blood levels of amprenavir (APV) alone, APV combined with efavirenz (EFV), and APV/EFV combined with a third drug (nelfinavir \[NFV\], indinavir \[IDV\], ritonavir soft gel capsules \[RTV sgc\], or saquinavir soft gel capsules \[SQV sgc\]). Anti-HIV therapy with 3 or 4 drugs is currently the recommended approach for treating HIV infections. Doctors need to know the best dosages of certain drugs when they are given in combination. This study will measure the blood levels of APV alone, APV combined with EFV, and APV/EFV plus a second PI in healthy volunteers. It will study the safety and tolerance of these drugs.