Strong CYP3A4 inhibitors (ketoconazole, itraconazole, clarithromycin, erythromycin, HIV protease inhibitors), CYP3A4 inducers (rifampicin, phenytoin, carbamazepine, St John"s wort), Verapamil, Diltiazem, Other heart-rate lowering drugs (beta-blockers, digoxin, amiodarone) increasing bradycardia risk, Grapefruit juice