Decreased clearance w/ cimetidine. Increased exposure w/ fluconazole, ketoconazole & amiodarone (CYP2C9 & CYP3A4 inhibitors). Increased clearance w/ rifampicin. Reports of some cases of menstrual disturbance when co-administered w/ OCs. Decreased clearance of caffeine (IV), desipramine & CYP2D6 substrates (eg, TCAs, β-blockers, SSRIs, antiarrhythmics, MAOIs). Increased metabolic ratio of dextromethorphan/dextrorphan in urine. Increase clearance of ciclosporin. Rare cases of changes in INR &/or prothrombin w/ warfarin.