Population pharmacokinetics of dolutegravir: influence of drug-drug interactions in a real-life setting

Objectives: Dolutegravir is widely prescribed owing to its potent antiviral activity, high genetic barrier and good tolerability. The aim of this study was to characterize dolutegravirs pharmacokinetic profile and variability in a real-life setting and to identify individual factors and co-medications affecting dolutegravir disposition. Methods: A population pharmacokinetic model was developed using NONMEM (R). Relevant demographic factors, clinical factors and co-medications were tested as potential covariates. Simulations based on the final model served to compare expected dolutegravir concentrations under standard and alternative dosage regimens in the case of drug-drug interactions. Results: A total of 620 dolutegravir plasma concentrations were collected from 521 HIV-infected individuals under steady-state conditions. A one-compartment model with first-order absorption and elimination best characterized dolutegravir pharmacokinetics. Typical dolutegravir apparent clearance (CL/F) was 0.93 L/h with 32% between-subject variability, the apparent volume of distribution was 20.2 L and the absorption rate constant was fixed to 2.24 h(-1). Older age, higher body weight and current smoking were associated with higher CL/F. Atazanavir co-administration decreased dolutegravir CL/F by 38%, while darunavir modestly increased CL/F by 14%. Rifampicin co-administration showed the largest impact on CL/F. Simulations suggest that average dolutegravir trough concentrations are 63% lower after 50 mg/12h with rifampicin compared with a standard dosage of 50 mg/24h without rifampicin. Average trough concentrations after 100 mg/24h and 100 mg/12h with rifampicin are 92% and 25% lower than the standard dosage without rifampicin, respectively. Conclusions: Patients co-treated with dolutegravir and rifampicin might benefit from therapeutic drug monitoring and individualized dosage increase, up to 100 mg/12 h in some cases.