Calcium channel blocker:A drug that blocks the entry ofcalciuminto themusclecells 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 thecontractionof the heart anddilate(widen) the arteries. Bydilatingthe arteries, CCBs reduce the pressureinthe arteries. This makes it easier for the heart to pumpblood, and, as a result, the heart needs lessoxygen. By reducing the heart's need for oxygen, CCBs prevent or relieve angina. CCBs also are used for treating high blood pressure because of theirblood 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 commonside effectsof CCBs are constipation, nausea, headache, rash, edema (swelling of the legs with fluid), low blood pressure, drowsiness, and dizziness. When diltiazem orverapamilare 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 ofcarbamazepine(Tegretol),simvastatin(Zocor),atorvastatin(Lipitor), andlovastatin(洛伐他汀). This can lead totoxicityfrom 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).
