Sensitive and specific determination of eight antiretroviral agents in plasma by high-performance liquid chromatography–mass spectrometry

Therapeutic drug monitoring of antiretroviral drugs has become more and more important. Therefore, a highly specific method is presented, which is capable of quantifying the different proteinase inhibitors (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir) and non-nucleoside reverse transcriptase inhibitors (efavirenz, nelfinavir). The antiretroviral agents were separated and detected using LC–MS and atmospheric pressure chemical ionization. After solid-phase extraction, the antiretrovirals were separated within 21 min using gradient elution. The calibration range of each drug was linear including the expected minimum and maximum concentrations measured in plasma after the administration of the different drugs. All within-day and between-day coefficients of variation were below 10% and the recovery rates were between 34.8 and 124%. The respective quantification limits were 1 μg/l (indinavir), 10 μg/l (amprenavir, efavirenz), 50 μg/l (saquinavir), 90 μg/l (nelfinavir), 200 μg/l (nevirapine, ritonavir) and 250 μg/l (lopinavir).