Single-Measurement Therapeutic Drug Monitoring of the HIV/AIDS Drugs Abacavir, Zidovudine, Lamivudine, Efavirenz, Nevirapine, Lopinavir and Nelfinavir

Background: There is currently no consensus about the significance of therapeutic drug monitoring (TDM) in the management of human immunodeficiency virus (HIV) infection. Objectives: In this study, single drug levels from routine clinical samples were determined in order to add further data on the therapeutic plasma level range and on drug levels under anti-HIV therapy in general. Materials and Methods: A total of 215 plasma samples obtained from patients with HIV infection for whom TDM was requested for the first time were evaluated. Plasma values were determined for abacavir and zidovudine between 1 and 3 h after drug intake. Lamivudine, efavirenz, nevirapine, lopinavir and nelfinavir plasma values were determined between 1 and 12 h after drug intake. Drug levels were determined with a home-brewed assay based on high-performance liquid chromatography. Results: Plasma concentrations of HIV drugs showed a large variability. Plasma concentrations of abacavir, zidovudine and lamivudine were found to be similar to those reported recently. For efavirenz and nevirapine, 37 and 61% of the samples did not meet the minimum trough levels suggested. For lopinavir and nelfinavir, the majority of the samples (78 and 80%) were found to be within the therapeutic plasma level range. Conclusion: Despite a large variation of anti-HIV drug plasma concentrations, single-measurement TDM may be sufficient in the routine management of the majority of patients.