About Labetalol A mixed alpha/beta Adrenergic antagonist, Antihypertensive(pregnancy-induced hypertension). Mechanism of Action of Labetalol Labetalol is an adrenergic antagonist capable of blocking alpha-1, beta-1, and beta-2 receptors and additional weak beta-2 agonistic action. It decreases heart rate, myocardial contraction, cardiac output, total peripheral resistance and B.P. Fall in B.P. is due to alpha-1 and beta-1 blockade as well as beta-2 agonism (vasodilatation). It also inhibits nor adrenaline uptake by adrenergic nerve endings. Indications for Labetalol 1. Phaeochromocytoma 2. Hypertensive emergencies 3. Clonidine withdrawal 4. All grades of hypertension 5. Cheese reaction 6. Late onset pregnancy hypertension Interactions for Labetalol Tricyclic antidepressants: Increased incidence of tremor. Cimetidine: Bioavailability of labetalol is enhanced.