Nifedipine in the Treatment of Cardiovascular Disease

Nifedipine, a calcium channel blocking agent, has been shown safe and effective in the treatment of various cardiac disorders. In Prinzmetal's variant angina, nifedipine relieves the acute spasm of a large coronary artery, and thereby reverses the sudden decrease in myocardial oxygen supply. In chronic stable angina, the efficacy of nifedipine stems from an interplay of direct and reflex effects. A decrease in systemic vascular resistance, and thus, myocardial oxygen demand, is considered the most important effect. Although this is partially offset by baroreceptor-mediated reflex increases in blood pressure and heart rate, the net effect is a decrease in myocardial oxygen consumption. The importance of nifedipine-induced increases in coronary blood flow in relieving stable angina remains controversial. Numerous clinical trials in patients with chronic angina have demonstrated that nifedipine increases exercise tolerance by lowering the heart rate-blood pressure product (an approximation of myocardial oxygen consumption). The maximal double product during exercise, however, does not increase, suggesting that the drug does not importantly improve myocardial oxygen supply. Nifedipine may also be of value in the therapy of unstable angina, acute myocardial infarction, and hypertension, as well as in the protection of the myocardium at risk during open heart surgery. However, definite recommendations on the use of the drug for these indications must await results of ongoing randomized studies. The effects of nifedipine are dose-related. Larger doses have been shown more effective than smaller doses, as long as an appropriate blood pressure is maintained. The side effects of nifedipine are mild and related to its vasodilating action.