Biol. Pharm. Bull. 28(7) 1286—1290 (2005)

ficiency virus (HIV)-1 infection has been advanced by the development of highly active antiretroviral therapy (HAART). HAART reduces plasma HIV-RNA below detectable limits in most cases. However, some patients do not have a sustainable antiviral response, even after experiencing a decrease in plasma HIV-RNA, due to the development of drug resistance and metabolic complications. This undesirable outcome may result from a failure to achieve effective antiretroviral drug plasma concentrations. Therefore, monitoring plasma drug concentrations is essential to ensure optimal drug efficacy, to prevent viral resistance, to manage drug interactions, to avoid adverse effects, and to assess nonadherence. In recent years several HPLC methods for simultaneous determination of antiretroviral drugs in plasma have been published. However, to popularize the simultaneous determination method, a simplified technique is necessary because the reported techniques require a solid-phase extraction, and/or use of a gradient elution, and/or an ultraviolet detection at multi wavelengths, all of which are not routinely available in conventional hospital laboratories. Therefore, we aimed to develop a simple procedure for simultaneous quantitative determination of seven protease inhibitors (PI): amprenavir (APV), atazanavir (ATV), indinavir (IDV), lopinavir (LPV), nelfinavir (NFV), ritonavir (RTV), saquinavir (SQV), and the nonnucleoside reverse transcription inhibitor, efavirenz (EFV), in human plasma. Our technique involves rapid liquid–liquid drug extraction from plasma, the use of an isocratic elution, as well as an ultraviolet detection at a single wavelength. This assay is based on our previously published HPLC method. MATERIALS AND METHODS