dofetilide + diltiazem

This is a combination of two pharmaceutical drugs, dofetilide and diltiazem. Dofetilide is a class III antiarrhythmic agent used primarily for the conversion and maintenance of normal sinus rhythm in patients with atrial fibrillation or atrial flutter. It works by selectively blocking the rapid component of the delayed rectifier potassium current (IKr), thereby prolonging cardiac action potential duration and refractory period[4][7]. Diltiazem is a non-dihydropyridine calcium channel blocker (class IV antiarrhythmic) that inhibits L-type calcium channels, leading to decreased heart rate, reduced myocardial contractility, and slowed conduction through the atrioventricular node. The combination of these two agents is not standard therapy due to significant pharmacokinetic interactions; diltiazem can increase plasma levels of dofetilide by inhibiting CYP3A4 and P-glycoprotein pathways, raising the risk for serious arrhythmias such as torsades de pointes[1][2][3][6].