LABETALOL AND OTHER AGENTS THAT BLOCK BOTH ALPHA-ADRENERGIC AND BETA-ADRENERGIC RECEPTORS

BACKGROUND Labetalol, a compound that blocks both alpha- and beta-adre nergic receptors, is the only drug of its class currently available in the United States. OBJECTIVE To review the pharmacology of labetalol and related compounds. SUMMARY Unlike ''pure'' beta blockers, labetalo l maintains cardiac output, reduces total peripheral resistance, and d oes not decrease peripheral blood flow. It has been used to treat hype rtension of all degrees of severity and may be especially useful in bl ack patients, elderly patients, patients with renal disease, and in pr egnancy. It can be used in conditions that produce catecholamine crise s, such as pheochromocytoma, clonidine withdrawal, and cocaine overdos e. Its hemodynamic profile is attractive for use in myocardial ischemi a. The parenteral form is useful in situations where blood pressure mu st be lowered quickly. The major side effect is orthostatic hypotensio n, and hepatotoxicity has been reported. CONCLUSIONS Labetalol has sev eral advantages over pure beta-blocking drugs and offers an alternativ e in managing hypertension that is difficult to control.