Risk factors contributing to a low darunavir plasma concentration

Darunavir is an efficacious drug; however, pharmacokinetic variability has been reported. The objective of this study was to find predisposing factors for low darunavir plasma concentrations in patients starting the once‐ or twice‐daily dosage. Darunavir plasma concentrations from January 2010 till December 2014 of human immunodeficiency virus‐infected individuals treated in the outpatient clinic of the University Medical Center Groningen were retrospectively reviewed. The first darunavir plasma concentration of patients within 8 weeks after initiation of darunavir therapy was selected. A dichotomous logistic regression analysis was conducted to select the set of variables best predicting a darunavir concentration below median population pharmacokinetic curve. In total 113 patients were included. The variables best predicting a darunavir concentration besides food intake included age together with estimated glomerular filtration rate (Hosmer–Lemeshow test P = 0.945, Nagelkerke R (2) = 0.284). Systematic evaluation of therapeutic drug monitoring results may help to identify patients at risk for low drug exposure.