Effect of ritonavir-boosted danoprevir, a potent hepatitis C virus protease inhibitor, on the pharmacokinetics of methadone in healthy subjects undergoing methadone maintenance therapy

Danoprevir: First Global Approval

Ascletis has developed danoprevir (Ganovo^®), an orally-administered hepatitis C virus NS3 protease inhibitor, as a treatment for hepatitis C. Based on positive results in phase II and phase III trials in patients with hepatitis C, danoprevir, in combination with ritonavir, peginterferon alfa and ribavirin was recently approved for marketing in China for the treatment of treatment-naive patients with non-cirrhotic genotype 1b chronic hepatitis C. This article summarizes the milestones in the development of danoprevir leading to this first approval.

Methadone Metabolism and Drug-Drug Interactions: In Vitro and In Vivo Literature Review

Methadone is utilized for the treatment of individuals with opiate dependence. Methadone undergoes N-demethylation by multiple cytochrome P450 (CYP) enzymes including CYP3A4, CYP2B6, CYP2C19, CYP2D6, CYP2C9, and CYP2C8. In vivo, polymorphism effects on methadone systemic exposure have been noted for CYP2B6, CYP3A4, and CYP2D6. Clinical drug interaction studies with antiviral drugs in methadone maintenance treatment patients yield varying results on methadone pharmacokinetics and pharmacodynamics. In general, CYP inhibitors altered methadone exposure with no adverse effects. CYP inducers generally decreased methadone exposure with some reports of withdrawal symptoms in the subjects. Interaction studies with antiviral drug combinations yielding differing results depend on the enzyme(s) affected. For certain antiviral medicines which are dual inhibitor(s) and inducer(s) for CYP enzymes, their effect on methadone pharmacokinetics can change with time since the effect of induction is usually delayed compared to the effect of inhibition.