Possible Interaction: Dextromethorphan and Quinidine

“AIMS To test the hypothesis that inhibition of cytochrome P450 2D6 (CYP2D6) by quinidine increases the antitussive effect of dextromethorphan (DEX) in an induced cough model.”

“Pretreatment of these subjects with 100 mg of quinidine , a selective inhibitor of CYP2D6, significantly suppressed the formation of dextrorphan and elevated the concentrations of dextromethorphan (t1/2, 16.4 hours).”

“These data demonstrated that the CYP2D6 phenotype and the concurrent administration of quinidine significantly affect the disposition of dextromethorphan and the formation of the active metabolite dextrorphan and are important factors to be considered in studies of the pharmacologic and behavioral effects of dextromethorphan.”

“Coadministration of DM with a low dose of quinidine inhibits DM metabolism, yields greater bioavailability and enables more specific testing of the therapeutic properties of DM apart from its metabolites.”

“In that group, in which standard diagnostic criteria were used to diagnose dementia, several pharmacologic agents were efficacious compared with placebo; however, only cannabinoids and the combination of dextromethorphan and quinidine had a clinically important effect.”

“In that group, in which standard diagnostic criteria were used to diagnose dementia, several pharmacologic agents were efficacious compared with placebo; however, only cannabinoids and the combination of dextromethorphan and quinidine had a clinically important effect.”

“Fixed-dose dextromethorphan/quinidine capsules (Nuedexta®) utilize quinidine to inhibit the metabolism of dextromethorphan , enabling high plasma dextromethorphan concentrations to be reached without using a larger dose of the drug.”

“ Quinidine inhibits the metabolism of dextromethorphan , reducing dextrorphan levels.”

“The combination of dextromethorphan and quinidine appears ineffective as a primary treatment for opioid withdrawal.”

“Blood levels of dextromethorphan , a nonnarcotic cough suppressant, are increased dramatically when it is coadministered with low dosages of quinidine , which inhibits its degradation.”

“ DM is currently being reintroduced as the active ingredient in a novel combination product in which low-dose quinidine is added to inhibit its breakdown, elevating blood levels of DM and increasing its likelihood of reaching neuronal targets2.”

“Recent evidence suggests that treatment with a fixed combination of dextromethorphan and the cytochrome P450 2D6 enzyme inhibitor, quinidine , can improve PBA.”