Calcium channel blockers in essential hypertension - Tips from Other Journals

Date: Sept, 1991

Although originally developed for the treatment of angina and supraventricular arrhythmias, calcium channel blockers have been shown to be effective in lowering systolic and diastolic blood pressure in patients with hypertension. Cummings and colleagues review the physiologic process of regulating blood pressure, the pharmacology of the calcium channel blockers and the appropriate application of these agents in the treatment of high blood pressure.

Calcium channel blockers interfere with the transmembrane flux of calcium, decrease vessel responsiveness to angiotensin II (at least acutely), may increase renin secretion, and promote a mild natriuresis and diuresis without compensatory sodium retention. They may also reduce glomerular hypertension in diabetic patients and decrease left ventricular hypertrophy by lowering blood pressure as well as by directly affecting the mycocardium.

Calcium channel blockers do not affect levels of blood glucose, insulin, uric acid or potassium. They may raise high-density lipoprotein cholesterol levels with no adverse effects on total serum cholesterol levels or triglyceride levels. Data from animal studies suggest that calcium channel blockers can suppress atherogenesis through an effect on calcium without affecting serum cholesterol levels. All of the classes of calcium channel blockers that are currently available are about equally effective in blood pressure control. However, the side effect profile of each drug differs.

Calcium channel blockers have an important role in patients who have not responded well to other monotherapy. They are useful in patients with concurrent diseases that may also respond to calcium antagonists, such as angina, Raynaud's disease or asthma. These drugs are also effective in patients who tend to have low plasma renin activity, such as black patients and elderly patients.

Patients usually respond to treatment with calcium antagonists within one or two weeks. However, physicians should wait four weeks before adding a second agent or discontinuing use of the drug. Compared with other antihypertensive drugs, calcium channel blockers are as effective as beta blockers and are as effective or superior to other drugs used in monotherapy, such as hydralazine, captopril, methyldopa, prazosin and enalapril. They may be used in combination with diuretics, methyldopa or captopril. Caution is advised when combining calcium channel blockers and beta blockers.

Nifedipine is generally well tolerated, but may produce a somewhat higher incidence of side effects than other calcium antagonists. These side effects include flushing, headache, peripheral edema and reflex tachycardia. The reactions may be attenuated or eliminated if nifedipine is taken with food or a sustained-release preparation is used. Reactions associated with cardiac negative inotropic effects (such as congestive heart failure) and electrophysiologic disturbances (such as atrioventricular block) are greatest with verapamil, moderate with diltiazem, and lowest with nifedipine and nicardipine. Gstrointestinal reactions are more common with verapamil.

The sustained-release preparations of calcium channel blockers are costly, but may enhance compliance since they need to be taken only once daily. (Archives of Internal Medicine, February 1991, vol. 151, p. 250.)

COPYRIGHT 1991 American Academy of Family PhysiciansCOPYRIGHT 2004 Gale Group

 
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