<p>May induce torsade de pointes or QT prolongation if co-administered with class IA (e.g. quinidine) or class III (e.g. amiodarone) antiarrhythmic agents, methadone, antipsychotics, moxifloxacin. Enhanced anticoagulant effect of warfarin. Increased adverse effects when used with drugs that may inhibit oxidation (e.g. cimetidine, ketoconazole). May increase serum levels of ciclosporin and Ca channel blockers.</p>