Drug	Result of interaction
Digoxin22	Elevated digoxin plasma concentration
Warfarin (Coumadin)21	Elevated prothrombin time
Simvastatin (Zocor)24	Increased incidence of myopathy when simvastatin dosage is higher than 20 mg per day
Sildenafil (Viagra)25	Increased sildenafil plasma concentration
Cyclosporine (Sandimmune)4	Increased cyclosporine plasma concentration
Antiarrhythmic drugs4	Additive effects: possible elevated plasma concentrations of quinidine, disopyramide (Norpace), flecainide (Tambocor), propafenone (Rythmol), and dofetilide (Tikosyn)
Quinolones23	Additive QT effect: possible increased risk of proarrhythmia
Antidepressants23	Increased plasma concentration of hepatically metabolized drugs: possible increased risk of proarrhythmia