How do calcium channel blockers help treat high blood pressure (BP)?

Calcium channel blockers, also called calcium antagonists, are a class of drugs that blocks the movement of calcium into the muscle cells of the heart and blood vessels. This causes the muscles to relax, lowering blood pressure, slowing the heart rate and decreasing oxygen demands of the heart. These medications lower blood pressure in patients with hypertension, but have little effect on normal blood pressure. Since they decrease the heart’s pumping strength, slow the heart rate and relax blood vessels, they are also used to treat other heart conditions, such as chest pain (angina) and abnormal heart rhythms (arrhythmias).

Calcium channel blockers (calcium antagonists) relax artery muscles and dilate coronary arteries and other arteries by blocking the transport of calcium into these structures, thus lowering blood pressure. There are two classes of calcium blockers; the dihydropyridines and the non-dihydropyridines:

• Non-dihydropyridines. These drugs help reduce chest pain (angina) and heart-rhythm irregularities such as atrial fibrillation. Some commonly prescribed drugs in this class include verapamil (Isoptin, Verelan, Calan) and diltiazem (Cardizem, Tiazac).
• Dihydropyridines. These drugs are also effective in treating patients with angina. They are sometimes used in treating systolic hypertension in elderly patients. Dihydropyridines generally have a weaker effect on the heart and some, such as amlodipine, take longer to work. But once they start working, they work well throughout the day, making them a good "once-a-day" drug. Some commonly prescribed drugs in this class include nifedipine (Adalat, Procardia and others), nicardipine (Cardene), isradipine (DynaCirc), amlodipine (Norvasc, Lotrel), and felodipine (Plendil). One dihydropyridine, fast-acting nifedipine, may increase your risk of heart attack when used for acute hypertension; therefore, nifedipine should only be used in the treatment of chronic high blood pressure. It is unclear whether other calcium channel blockers share this risk, so discuss this and other potential risks with your healthcare professional if you receive a prescription for a calcium channel blocker.

Dihydropyridines also may cause ankle swelling, rapid heartbeat and headaches and may make you flush.