What is the classification of Verapamil (calcium channel blocker)?

Classification of Verapamil

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, 2

Pharmacological Classification Details

• Verapamil belongs to the phenylalkylamine subclass of calcium channel blockers, which is distinct from dihydropyridines (like amlodipine) and benzothiazepines (like diltiazem) 1, 3
• It functions as a calcium ion influx inhibitor (slow-channel blocker or calcium ion antagonist) that modulates the influx of ionic calcium across cell membranes 2
• Verapamil inhibits calcium influx through L-type calcium channels located in:
  • Arterial smooth muscle
  • Cardiac myocytes (contractile cells)
  • Cardiac conduction tissue 1, 2

Pharmacological Effects

• Verapamil has less selectivity for vasculature compared to dihydropyridine CCBs 1
• It produces more pronounced effects on:
  • Myocardial contractility (negative inotropic effect)
  • Cardiac pacemaker function
  • Atrioventricular conduction (negative chronotropic and dromotropic effects) 1
• It causes coronary and peripheral arterial vasodilation 2
• Verapamil has antiarrhythmic properties, particularly for supraventricular tachyarrhythmias 1, 4
• It has local anesthetic properties approximately 1.6 times that of procaine on an equimolar basis 2

Clinical Applications

• Treatment of hypertension through decreased systemic vascular resistance 2, 5
• Management of angina pectoris, including vasospastic (Prinzmetal's) angina 1, 2
• Treatment of supraventricular tachyarrhythmias 1
• Used in atrial fibrillation and flutter for rate control 1

Pharmacokinetic Properties

• Verapamil is metabolized in the liver by cytochrome P450 3A4 1
• More than 90% of orally administered verapamil is absorbed 2

Important Clinical Considerations

• Verapamil should not be used in combination with ivabradine due to risk of severe bradycardia 1
• It is contraindicated in patients with:
  • Significant left ventricular dysfunction
  • Increased risk for cardiogenic shock
  • PR interval greater than 0.24 second
  • Second or third-degree atrioventricular block without a cardiac pacemaker 1
• Common adverse effects include:
  • Constipation (especially in elderly individuals)
  • Hypotension
  • Bradycardia
  • Leg edema 1, 3

Distinguishing Features from Other Calcium Channel Blockers

• Unlike dihydropyridine CCBs (amlodipine, nifedipine), verapamil has significant effects on cardiac conduction and contractility 1, 6
• Verapamil and diltiazem (non-dihydropyridines) are more myocardial-selective, while dihydropyridines are more vascular-selective 6
• Some research suggests verapamil may also have beta-blocking properties, though this is not its primary mechanism 7