Simultaneous quantitative assay of six HIV protease inhibitors, one metabolite, and two non-nucleoside reverse transcriptase inhibitors in human plasma by isocratic reversed-phase liquid chromatography

A rapid (less than 30 min), sensitive, and specific liquid chromatography method for simultaneous assay of nine antiretroviral drugs in human plasma is described. This technique allows therapeutic drug monitoring of six approved protease inhibitors (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir) and two approved non-nucleoside reverse transcriptase inhibitors (efavirenz and nevirapine). Assays were performed after diethyl ether liquid-liquid extraction from 250-muL plasma samples. Chromatographic separation was achieved on an X-TERRA (Waters Saint Quentin, France) column using a 58% water (with 3 mmol/L pyrrolidine) and 42% acetonitrile mobile phase. Three ultraviolet wavelengths were used for detection with a diode array detector. This method allowed quantitative assay of all nine antiretroviral drubs within a concentration range of 25 ng/mL to 9000 ng/mL. The method has been validated extensively and has been in routine use in our laboratory for several months for drug monitoring in plasma samples from patients treated with antiretroviral drugs.