Calcium channel blockers prevent calcium from entering cells of the heart and blood vessel walls. This results in lower blood pressure. Calcium channel blockers, also called calcium antagonists, relax and widen blood vessels by affecting the muscle cells in the arterial walls.

Some of the medications in this class have the added benefit of slowing your heart rate, which can further lower blood pressure.

There are two types of calcium channel blockers: short-acting and long-acting. Short-acting medications work quickly, but their effects last only a few hours. Long-acting medications take longer to start working, but their effects last longer.

Several calcium antagonists are available. Which one is best for you depends on your health and the condition being treated.

Examples of calcium antagonists include:

• Amlodipine (Norvasc)
• Diltiazem (Cardizem, Dilacor XR)
• Nifedipine (Adalat, Procardia)
• Verapamil (Calan, Isoptin, Verelan, Covera)

Under special circumstances, your doctor might prescribe a calcium channel blocker along with other high blood pressure drugs or with cholesterol-lowering drugs such as statins.

Doctors prescribe calcium channel blockers to prevent, treat or improve symptoms in a variety of conditions, such as:

• High blood pressure
• Chest pain (angina)
• Migraines
• Brain aneurysm complications
• Irregular heartbeats (arrhythmia)
• Raynaud's disease
• Pulmonary hypertension

Side effects of calcium channel blockers include constipation, headache, rapid heartbeat, rash, drowsiness, flushing, nausea, and swelling in the feet and lower legs.

Certain calcium channel blockers interact with grapefruit products. Don't take these medications with grapefruit or grapefruit juice because they can reduce your liver's ability to eliminate calcium channel blockers from your body, allowing the medications to build up in your body.