Study objective: To investigate the steady-state pharmacokinetics of methadone when coadministered with ritonavir-boosted danoprevir (DNVr).
Design: Open-label, two-period, single-sequence pharmacokinetic study.
Setting: Two U.S. research centers.
Patients: Eighteen methadone-maintained healthy adults.
Measurements and main results: In Period 1 (Day -1), subjects received their daily methadone maintenance therapy (MMT). In Period 2 (Days 1-10), subjects received MMT plus DNVr 100/100 mg twice/day. Pharmacokinetic parameters for the total concentrations of (R)- and (S)-methadone on Days -1 and 10 were determined using noncompartmental methods. Unbound (R)- and (S)-methadone concentrations at 3 hours postdose were also assessed on Days -1 and 10. Geometric mean ratios (GMRs) and 90% confidence intervals (CIs) were used to compare steady-state (R)- and (S)-methadone pharmacokinetics when MMT was administered with or without DNVr. Methadone withdrawal was assessed using the Subjective Opiate Withdrawal Scale. Compared with MMT alone, methadone AUCtau and Cmax GMR (90% CI) following coadministration with DNVr were 1.02 (0.91-1.15) and 1.01 (0.90-1.13) for (R)-methadone, and 1.01 (0.90-1.13) and 0.99 (0.89-1.10) for (S)-methadone, respectively. Unbound (R- and (S)-methadone concentrations were comparable with or without DNVr. No instances of methadone withdrawal were reported. MMT in combination with DNVr was well tolerated.
Conclusion: Coadministration of DNVr with MMT resulted in no significant pharmacokinetic interactions or signs of methadone withdrawal. No dosage adjustment is needed for MMT when coadministered with DNVr.
Keywords: HCV; methadone maintenance; pharmacokinetics; ritonavir-boosted danoprevir.
© 2013 Pharmacotherapy Publications, Inc.