Labetalol and other agents that block both alpha- and beta-adrenergic receptors

BACKGROUND Labetalol, a compound that blocks both alphaand beta-adrenergic 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, labetalol maintains cardiac output, reduces total peripheral resistance, and does not decrease peripheral blood flow. It has been used to treat hypertension of all degrees of severity and may be especially useful in black patients, elderly patients, patients with renal disease, and in pregnancy. It can be used in conditions that produce catecholamine crises, such as pheochromocytoma, clonidine withdrawal, and cocaine overdose. Its hemodynamic profile is attractive for use in myocardial ischemia. The parenteral form is useful in situations where blood pressure must be lowered quickly. The major side effect is orthostatic hypotension, and hepatotoxicity has been reported.

CONCLUSIONS Labetalol has several advantages over pure beta-blocking drugs and offers an alternative in managing hypertension that is difficult to control.