Assessment of the pharmacokinetics of co-administered maraviroc and raltegravir

AIMS To assess the two-way pharmacokinetic interaction between maraviroc and raltegravir. METHODS In this open-label, multiple-dose, fixed-sequence study, 18 healthy, human immunodeficiency virus (HIV)-seronegative subjects received the following: days 1-3 raltegravir 400 mg q12h, days 4-5 washout, days 6-11 maraviroc 300 mg q12h, and days 12-14 raltegravir 400 mg q12h + maraviroc 300 mg q12h. Serial 12-h blood samples were collected on days 3 (raltegravir), 11 (maraviroc) and 14 (raltegravir + maraviroc). Plasma samples were assayed by validated liquid chromatography tandem mass spectrometry assays. Test/reference ratios and 95% confidence intervals (CIs) were determined for pharmacokinetic parameters. RESULTS For maraviroc, the test/reference % ratio (95% CI) for AUC(tau), was 85.8 (78.7, 93.5), for C-max was 79.5 (64.8, 97.5) and for C-min was 90.3 (84.2, 96.9). For raltegravir, the test/reference % ratio (95% CI) for AUC(tau) was 63.3 (41.0, 97.6), for C-max was 66.8 (37.1, 120.0) and for C-min was 72.4 (55.1, 95.2). In all subjects, maraviroc average concentrations (AUC(tau) divided by 12) were >1 00 ng ml(-1), the threshold value below which there is an increased risk of virological failure. Based on clinical experience for raltegravir, mean C-min decreases >60% are considered to be clinically relevant for short-term activity; however, in the present study mean changes were only 28% and thus not considered to be of clinical relevance. CONCLUSIONS Co-administration of maraviroc and raltegravir decreased systemic exposure of both drugs; however, these are not likely to be clinically relevant. Safety and efficacy studies may help in understanding the role of this combination in the treatment of HIV infection.