- Clinical science
Calcium channel blockers (CCBs) are drugs that bind to and block the L-type calcium channel. The L-type channels are the predominant calcium channels in the myocardium and the vascular smooth muscles. By blocking these channels, CCBs cause peripheral arterial vasodilation and myocardial depression, which leads to a drop in blood pressure and negative chronotropic, inotropic, and dromotropic effects on the myocardium. The most common indications for CCB use are hypertension, angina, and supraventricular arrhythmias. CCBs are also beneficial in the treatment of cardiomyopathy, thromboangiitis obliterans, Raynaud's phenomenon, and cluster headaches. CCBs are divided into three classes based on their effects: dihydropyridines (e.g., nifedipine, amlodipine) are potent vasodilators, phenylalkylamines (verapamil, gallopamil) are potent myocardial depressants, and benzothiazepines (diltiazem) are moderate vasodilators and myocardial depressants. The main side effects of dihydropyridines are caused by vasodilation (headaches, peripheral edema, reflex tachycardia), and those of phenylalkylamines by myocardial depression (bradyarrhythmias, atrioventricular block). The side effects of benzothiazepines are generally similar but milder compared to those of the other CCB classes. CCBs are contraindicated in patients with pre-existing cardiac conduction disorders (e.g., atrioventricular block, sick sinus syndrome), symptomatic hypotension, and acute coronary syndrome.
|Class of CCB||Examples||Effects|
- CCBs bind to and block L-type calcium channels → 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
Phenylalkylamines (verapamil) primarily affect the calcium channels of the heart and are contraindicated in cases of heart failure because of their negative effect on myocardial contractility!
We list the most important adverse effects. The selection is not exhaustive.
- Common indications for CCBs
Less common indications
- All classes of CCB
- Benzothiazepines and phenylalkylamines
We list the most important contraindications. The selection is not exhaustive.