Diltiazem Classification
Diltiazem is a nondihydropyridine calcium channel antagonist (Class IV antiarrhythmic agent). 1, 2
Drug Classification Details
Diltiazem functions as a calcium ion cellular influx inhibitor (also called a slow channel blocker or calcium antagonist) 3. It specifically inhibits the influx of calcium ions during membrane depolarization of cardiac and vascular smooth muscle 3.
Antiarrhythmic Classification
Within the Vaughan Williams classification system for antiarrhythmic drugs:
- Class IV antiarrhythmic drugs include the calcium channel blockers verapamil and diltiazem 4
- These agents work by decreasing sinoatrial and atrioventricular conduction 3
- They are distinct from:
- Class I agents (sodium channel blockers like flecainide)
- Class II agents (beta-blockers)
- Class III agents (amiodarone, sotalol)
Mechanism of Action
Diltiazem interferes with the slow inward (depolarizing) current in excitable tissue and causes excitation-contraction uncoupling in myocardial tissues 3. It:
- Prolongs AV node functional and effective refractory periods
- Decreases sinoatrial and atrioventricular conduction
- Produces relaxation of coronary vascular smooth muscle
- Has negative chronotropic effects (slows heart rate)
Clinical Context
The ACC/AHA/HRS guidelines specifically categorize diltiazem under "Nondihydropyridine calcium channel antagonists" for acute management of supraventricular tachycardia 1, 2. This distinguishes it from dihydropyridine calcium channel blockers (like amlodipine or nifedipine), which lack significant antiarrhythmic properties and primarily cause vasodilation.