Hypertension Blog

By interfering with calcium ion influx across the cell membrane, calcium channel blockers inhibit calcium-dependent contraction of vascular smooth muscle. This decreases total peripheral vascular resistance and after load, which reduces blood pressure.Calcium channel blockers include diltiazem hydrochloride, felodipine, nicardipine, nifedipine, and verapamil.

Indications and Contraindications

Physicians commonly prescribe these drugs to treat patients with angina pectoris. However, several oral forms are used to treat vasospasm and mild to moderate hypertension. Parenteral forms are used to treat hypertension, atrial fibrillation, atrial flutter, and paroxysmal supraventricular tachycardia. But sustained-release nifedipine is only used to treat hypertension.

Use calcium channel blockers cautiously in patients with heart failure, hypotension, hepatic injury, and renal disease. Do not administer a calcium channel blocker to patients with sick sinus syndrome, second-degree or third-degree heart block, hypotension, acute MI, or pulmonary congestion. Do not administer verapamil to patients with cardiogenic shock or severe heart failure, and administer it cautiously to patients taking beta-blockers.

Adverse Effects and Interactions

The most serious adverse effects of calcium channel blockers include cardiovascular changes such as hypotension, arrhythmias, and worsened eart failure. Other common effects include headache, dizziness, flushing, weakness, and persistent peripheral edema. Your patient may also experience nausea, vomiting, diarrhoea, muscle fatigue, cramps, worsened angina, skin eruptions, photosensitivity, pruritus, nasal congestion, and mood changes.

Calcium channel blockers can interact with beta-blockers, causing heart block and heart failure. When diltiazem is taken with cimetidine, its effect increases. And when it’s administered with cimetidine or ranitidine, felodipine levels increase. Nicardipine increases the effects of digitalis glycosides, neuromuscular blockers, and theophylline. And when nifedipine is administered in combination with theophylline, beta­blockers, other antihypertensives, or digitalis glycosides, it increases their effects.

Quinidine decreases the effects of nifedipine. The hypotensive effects of verapamil increase when the drug is given with prazosin and quinidine. Verapamil also decreases the effects of lithium and increases the blood levels of digoxin, theophylline, cyclosporine, and carbamazepine. Verapamil is incompatible with albumin, amphotericin B, ampicillin, dobutamine, hydralazine, mezlocillin, nafcillin, oxacillin, and sodium bicarbonate.