Simultaneous determination of the HIV-protease inhibitors indinavir, amprenavir, ritonavir, saquinavir and nelfinavir in human plasma by reversed-phase high-performance liquid chromatography

A rapid, simple and sensitive high-performance liquid chromatographic (HPLC) assay has been developed for the simultaneous quantification of the HIV-protease inhibitors indinavir, amprenavir, ritonavir, saquinavir and nelfinavir in human plasma. The method involved the solid-phase extraction of the five drugs and the internal standard (I.S., verapamil) from 400 μl of human plasma. The HPLC analysis used a reversed-phase C₁₈ analytical column and a mobile phase consisting of a gradient with 15 mM phosphate buffer (pH 5.75)–acetonitrile and UV monitoring. The method was linear over the therapeutic concentration range for the five HIV-protease inhibitors. The accuracy of the method ranged from 98.2 to 106.7% and the precision values ranged from 1.4 to 8.1% for intra-day precision and from 3.1 to 6.4% for the inter-day values.