Plasma trough concentrations of darunavir/ritonavir and raltegravir in older patients with HIV-1 infection

Objectives The aim of the study was to assess plasma concentrations of darunavir/ritonavir and raltegravir in older patients compared with younger patients with HIV-1 infection. Methods In this observational, open-label study, adult HIV-infected out-patients aged <= 40 years (younger patients) or >= 60 years (older patients) and treated with tenofovir/emtricitabine plus darunavir/ritonavir (800/100 mg daily) or raltegravir (400 mg twice daily) were asked to participate. The trough concentrations (C-trough) of darunavir/ritonavir and raltegravir were assessed at steady state using a validated high-performance liquid chromatography (HPLC)-tandem mass spectrometry method. Results A total of 88 HIV-positive patients were enrolled in the study. Forty-six patients were treated with darunavir/ritonavir, and 42 with raltegravir. The geometric mean plasma C-trough (coefficient of variation) of raltegravir was comparable between the 19 older and 23 younger subjects: 106 ng/mL (151%) and 94 ng/mL (129%), respectively [geometric mean ratio (GMR) 0.85; 95% confidence interval (CI) 0.71-1.57; P = 0.087]. In contrast, the geometric mean plasma C-trough of darunavir was significantly higher among the 21 older patients [2209 ng/mL (139%)] than among the 25 younger patients [1876 ng/mL (162%); GMR 1.56; 95% CI: 1.22-1.88; P = 0.004]. Similarly, the geometric mean C-trough of ritonavir was significantly higher among older than among younger individuals. Conclusions The mean plasma C-trough of darunavir and ritonavir was significantly higher in older patients than in younger patients with HIV-1 infection, while the mean plasma level of raltegravir was comparable in the two groups. However, both regimens showed good tolerability in both younger and older subjects.