Calcium Channel Blockers

Mechanism of Action

Calcium channel blockers are a group of medications that act to inhibit either central or peripheral calcium channels. This results in decreased calcium influx and smooth muscle relaxation.

Dihydropyridine calcium channel blockers act predominantly in the periphery, causing arterial vasodilation.

Non-dihydropyridine calcium channel blockers act predominantly centrally to decrease heart rate (chronotropy) and contractility (inotropy).

Indications

Calcium channel blockers are used to treat hypertension and stable angina.

Non-dihydropyridine calcium channel blockers are used to lower heart rate during tachyarrhythmias, especially atrial fibrillation and atrial flutter, as well as during acute coronary syndromes when beta-blockers are contraindicated.

Verapamil has been studied to treat hypertrophic obstructive cardiomyopathy, as well as multifocal atrial tachycardia.

Names

• Dihydropyridine: amlodipine, nifedipine and felodipine.
• Non-dihydropyridine: diltiazem and verapamil.

Common reactions

• hypotension;
• dizziness;
• weakness and fatigue;
• bradycardia; and
• constipation (verapamil).

Miscellaneous

Sublingual dihydropyridine calcium channel blockers such as nifedipine historically were used for angina and hypertensive emergencies; however, they have been shown to increase stroke (likely due to sudden severe drop in blood pressure), myocardial infarction and death. Their use has been abandoned except in autonomic dysreflexia in spinal cord injury.

Verapamil-sensitive ventricular tachycardia is a known entity.