Intracellular and plasma steady‐state pharmacokinetics of raltegravir, darunavir, etravirine and ritonavir in heavily pre‐treated HIV‐infected patients

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • The combination of raltegravir, etravirine and ritonavir boosted darunavir is a potent antiretroviral regimen for patients who have been heavily pre‐treated for HIV‐infection. All these agents have to exert their action intracellularly. However, only little is known about the cellular pharmacology of these agents. WHAT THIS STUDY ADDS • We investigated the steady‐state plasma and cellular pharmacokinetics of raltegravir, etravirine, darunavir and ritonavir and the observed distinct intracellular accumulation ratios indicated that these antiretroviral drugs have different affinity for the cellular compartment. AIM To study the steady‐state plasma and intracellular pharmacokinetics of raltegravir, etravirine, darunavir and ritonavir in heavily pre‐treated patients. METHODS Patients on a salvage regimen containing raltegravir, etravirine, darunavir and ritonavir were eligible for inclusion. During a 12 h dosing interval plasma and peripheral blood mononuclear cells were collected. Drug concentrations were measured using a validated LC‐MS/MS assay and pharmacokinetic analysis was performed using non‐linear mixed effect modelling. RESULTS Irregular absorption was observed with raltegravir and darunavir, which may be caused by enterohepatic cycling. Relative bioavailability of ritonavir was low, when compared with other ritonavir regimens. Raltegravir plasma pharmacokinetics showed wide interpatient variability, while intracellular raltegravir concentrations could not be detected (