Calcium channel blockers (CCBs) are drugs that bind to and block L-type calcium channels, which are the predominant calcium channels in the myocardium and vascular smooth muscles. By blocking these channels, CCBs cause peripheral arterial vasodilation (leading to a drop in blood pressure) and myocardial depression (leading to negative chronotropic, inotropic, and dromotropic effects on the myocardium). CCBs are classified into two major groups according to the main site of action: Dihydropyridines (e.g., nifedipine, amlodipine) are potent vasodilators, and nondihydropyridines (e.g., verapamil) are potent myocardial depressants. Diltiazem, a common nondihydropyridine, has moderate vasodilatory and myocardial depressant effects. Nondihydropyridines are also categorized as class IV antiarrhythmic drugs and are used in the treatment of supraventricular arrhythmias. The most common indications for CCB use are arterial hypertension and stable angina. The main side effects of dihydropyridines are caused by vasodilation (e.g., headache, peripheral edema); those of nondihydropyridines are caused by myocardial depression (e.g., bradyarrhythmias, atrioventricular block). CCBs are contraindicated in patients with pre-existing cardiac conduction disorders, symptomatic hypotension, and/or acute coronary syndrome.
|Overview of calcium channel blockers |
|Dihydropyridines || |
- CCBs bind to and block L-type calcium channels in cardiac and vascular smooth muscle cells → decreased frequency of Ca2+ channel opening in response to cell membrane depolarization → decreased transmembrane Ca2+ current
Effects of decreased Ca2+ influx
- Vascular smooth muscle relaxation → vasodilation → decreased peripheral vascular resistance → decreased afterload → decreased blood pressure
- Decreased cardiac muscle contractility (negative inotropic action) → decreased cardiac output → decreased blood pressure
- Decreased SA node discharge rate (negative chronotropic action) → decreased heart rate (bradycardia) → decreased cardiac output → decreased blood pressure
- Decreased AV node conduction (negative dromotropic action) → termination of
- Dihydropyridines act mainly on vascular smooth muscle. The order of potency is nifedipine/amlodipine > verapamil > diltiazem.
- Nondihydropyridines act mainly on the heart. The order of potency is verapamil > diltiazem > amlodipine/nifedipine.
Verapamil mainly acts on Ventricles and Amlodipine mainly acts on Arteries.
- All CCBs 
Effects due to vasodilation
- Peripheral edema (esp. amlodipine)
- Headaches, dizziness
- Facial flushing, feeling of warmth
- Reflex tachycardia: a condition of tachycardia secondary to a decrease in blood pressure (esp. nifedipine)
- Gingival hyperplasia
- Effects due to vasodilation
- Nondihydropyridine 
We list the most important adverse effects. The selection is not exhaustive.
- All CCBs 
- Nondihydropyridines 
Phenylalkylamines (e.g., verapamil), which primarily affect the calcium channels of the heart, are contraindicated in cases of heart failure because of their negative effect on myocardial contractility.
We list the most important contraindications. The selection is not exhaustive.