Calcium channel blocker: A drug that blocks the entry of calcium into the muscle cells of the heart and the arteries. It is the entry of calcium into these cells that causes the heart to contract and arteries to narrow. By blocking the entry of calcium, calcium channel blocker (CCBs) decrease the contraction of the heart and dilate (widen) the arteries. By dilating the arteries, CCBs reduce the pressure in the arteries. This makes it easier for the heart to pump blood, and, as a result, the heart needs less oxygen. By reducing the heart's need for oxygen, CCBs prevent or relieve angina. CCBs also are used for treating high blood pressure because of their blood pressure-lowering effects. CCBs also slow the rate at which the heart beats and are therefore used for treating certain abnormal heart rhythms such as atrial fibrillation.
The most common side effects of CCBs are constipation, nausea, headache, rash, edema (swelling of the legs with fluid), low blood pressure, drowsiness, and dizziness. When diltiazem or verapamil are given to individuals with heart failure, symptoms of heart failure may worsen because these drugs reduce the ability of the heart to pump blood.
Most of the interactions of CCBs occur with verapamil or diltiazem. The interaction occurs because verapamil and diltiazem decrease the elimination of a number of drugs by the liver. Through this mechanism, verapamil and diltiazem may reduce the elimination and increase the blood levels of carbamazepine (Tegretol), simvastatin (Zocor), atorvastatin (Lipitor), and lovastatin (Mevacor). This can lead to toxicity from these drugs.
The CCBS that have been approved for use in the US include nisoldipine (Sular), nifedipine (Adalat, Procardia), nicardipine (Cardene), bepridil (Vascor), isradipine (Dynacirc), nimodipine (Nimotop), felodipine (Plendil), amlodipine (Norvasc), diltiazem (Cardizem), and verapamil (Calan, Isoptin).
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