Role of calcium antagonists in the treatment of essential hypertension.

The calcium antagonists, diltiazem and nifedipine, are effective in mild-to-moderate chronic essential hypertension. The overall responder rate is 80%. Diastolic blood pressure is lowered by 10-15% at rest and during exercise. Systolic blood pressure is reduced only at rest. Heart rate may be unchanged by nifedipine and lowered by diltiazem. Both drugs lead to a decrease of peripheral resistance by 15-20% at rest and 30% during work. As a consequence of afterload reduction, cardiac output, stroke index, and stroke work index increased by 17, 21, and 7% with nifedipine and 34, 26, and 20% with diltiazem. During exercise, these changes are even more pronounced. However, pulmonary artery pressure and pulmonary vascular resistance are reduced only by nifedipine, not by diltiazem. Presumably due to this combined preload and afterload reduction, nifedipine therapy is associated with a reflex activation of the sympathetic nervous system in all cases, with an increase in norepinephrine plasma concentration and, sometimes, tachycardia. Diltiazem, however, has the advantage of being a potent blood pressure-lowering agent, with afterload reduction and increased stroke index, with less pronounced catecholamine increase, and without tachycardia. Side effects with this drug are rare, and long-term therapy is well tolerated.