What class is Verapamil (calcium channel blocker)?

Verapamil Classification and Pharmacology

Verapamil is classified as a non-dihydropyridine calcium channel blocker (CCB) that specifically inhibits calcium influx through the high-voltage-activated L-type calcium channel. 1

Mechanism of Action

• Verapamil is a calcium ion influx inhibitor (slow-channel blocker or calcium ion antagonist) that exerts its pharmacologic effects by modulating the influx of ionic calcium across cell membranes of arterial smooth muscle and myocardial cells 2
• It belongs to the phenylalkylamine subclass of calcium channel blockers, which is distinct from dihydropyridines (like amlodipine) and benzothiazepines (like diltiazem) 1
• Unlike dihydropyridine CCBs, verapamil has less selectivity for vasculature, resulting in more pronounced effects on myocardial contractility and cardiac conduction 1

Pharmacological Effects

• Verapamil produces negative inotropic (decreased contractility), chronotropic (decreased heart rate), and dromotropic (decreased conduction velocity) effects on the heart 1
• It particularly affects atrioventricular (AV) node conduction by decreasing calcium influx and prolonging the effective refractory period within the AV node 2
• Verapamil dilates the main coronary arteries and coronary arterioles in both normal and ischemic regions, making it effective for vasospastic angina 2
• It reduces total systemic resistance (afterload) by dilating peripheral arterioles 2

Clinical Applications

• Verapamil is used in the management of:
  • Supraventricular tachyarrhythmias, including atrial fibrillation and flutter for rate control 3, 4
  • Angina pectoris, including vasospastic (Prinzmetal's) and unstable angina 1, 2
  • Hypertension, through its vasodilatory effects 2

Important Clinical Considerations

• Verapamil is contraindicated in patients with:
  • Severe left ventricular dysfunction or heart failure 4
  • Second or third-degree AV block without a pacemaker 4
  • Severe hypotension 4
  • Obstructive hypertrophic cardiomyopathy with severe dyspnea at rest or very high resting gradients (>100 mm Hg) 3
• It should not be used in combination with beta-blockers due to risk of profound bradycardia and hypotension 4
• Common side effects include constipation, hypotension, bradycardia, and leg edema 1, 5

Differences from Other Calcium Channel Blockers

• Unlike dihydropyridine CCBs (such as amlodipine), verapamil has more pronounced cardiac effects and less selective vasodilatory effects 1, 6
• Verapamil and diltiazem (non-dihydropyridine CCBs) should be avoided in patients with pulmonary edema or severe left ventricular dysfunction, while amlodipine is better tolerated in these patients 6

Verapamil's unique pharmacological profile makes it particularly useful for managing supraventricular arrhythmias and certain types of angina, but requires careful consideration of contraindications due to its significant cardiac effects.