Properties of Labetalol, a Combined Alpha- and Beta-blocking Agent, Relevant to the Treatment of Myocardial Ischemia

Labetalol, a combined alpha-beta-adrenergic antagonist, is one of the new group of beta-adrenergic blockers reduces peripheral and coronary vascular resistances while preserving cardiac output. Unlike alpha-adrenergic blockers, labetalol tends to reduce heart rate during rest and exercise. The drug is a potent antihypertensive agent which has been used by mouth and by vein to treat mild, moderate, and severe hypertension, including hypertensive emergencies. Labetalol has a hemodynamic profile which makes it an attractive agent for treating myocardial ischemia. The drug reduces blood pressure, left ventricular wall tension, heart rate, and contractility while preserving or even augmenting coronary blood flow. Studies with labetalol in hypertensive patients with angina have shown it to be more effective than placebo in reducing angina attacks and blood pressure while improving exercise tolerance. The drug appears to have antianginal and antihypertensive effects comparable to atenolol and propranolol. Side effects of treatment are observed and most are related to alpha- and beta-adrenergic blockade. Labetalol also appears to be effective for treatment of normotensive patients with angina and for silent myocardial ischemia. It has no apparent effects on serum lipids and lipoproteins. Labetalol appears to be a useful drug for treating the hypertensive heart and its many complications.