Some clinical trials suggest raltegravir may cause a modest decrease in darunavir plasma concentrations. At present the effect of raltegravir on darunavir plasma concentrations does not appear to be clinically relevant; darunavir/cobicistat and raltegravir can be used without dose adjustments.

Clinically relevant drug-drug interactions are not anticipated with concomitant use of darunavir and cobicistat with raltegravir.

Darunavir trough concentrations were determined in 117 samples from 55 HIV+ patients receiving darunavir containing regimens with either a NRTI or raltegravir. Mean (± sd) darunavir concentrations were higher in the NRTI subjects than in the raltegravir subjects (4.20 ± 2.35 vs 2.63 ± 84 mg/L). However, the proportion of subjects with undetectable viral loads (<50 copies/ml) was higher in the raltegravir group than in the NRTI group. After adjusting for time from last drug intake and concomitant drugs, a multivariate linear regression model confirmed raltegravir to be independently related to lower darunavir concentrations. The mechanism of this unexpected interaction remains to be determined, but it does not appear to be virologically significant.