Variability in non-nucleoside reverse transcriptase and protease inhibitors concentrations among HIV-infected adults in routine clinical practice.

Methods: The study included 117 patients who attended our clinic for routine outpatient blood tests and who were receiving antiretroviral therapy which included NNRTI or PI. Patients were not informed that drug concentrations were going to be assessed until blood sampling. The time of the last antiretroviral treatment intake and blood sampling were recorded. Drug concentrations were considered optimal if they were above the proposed minimum effective concentration. In addition, efavirenz, nevirapine and atazanavir concentrations were considered potentially toxic if they were higher than 4.0 mg l(-1), 6.0 mg l(-1), and 0.85 mg l(-1), respectively.

Results: Overall, interindividual variability in NNRTI and PI plasma concentrations was approximately 50%, and only 68.4% of the patients had drug concentrations within the proposed therapeutic range. Inappropriate adherence only explained 35% of subtherapeutic drug concentrations.

Conclusion: Overall, interindividual variability in NNRTI and PI plasma concentrations was approximately 50%, and only 68.4% of the patients had drug concentrations within the proposed therapeutic range. Inappropriate adherence only explained 35% of subtherapeutic drug concentrations.