Labetalol (LBT)

Labetalol is a mixed alpha/beta adrenergic antagonist, which is used to treat high blood pressure. Labetalol has relative contraindications for use in patients with asthma, congestive heart failure, any degree of heart block, bradycardia, hypotension or those in cardiogenic shock. For adrenergic agents, when the substituent on the amine nitrogen is greater in size than a t-butyl group, then the molecule typically is found to have receptor affinity without intrinsic activity, and is therefore an antagonist. Labetalol has two chiral carbons and consequently exists as four stereoisomers. Labetalol acts by blocking alpha and beta adrenergic receptors, resulting in decreased peripheral vascular resistance without significant alteration of heart rate or cardiac output.Labetalol combines both selective, competitive, alpha-1-adrenergic blocking and nonselective, competitive, beta-adrenergic blocking activity in a single substance.