labetalol

Labetalol is a medication used to treat hypertension and to manage hypertensive emergencies. It is a combined alpha-1 adrenergic receptor antagonist and nonselective beta-adrenergic blocker. By blocking alpha-1 receptors, it reduces peripheral vascular resistance, while beta-blockade decreases heart rate and myocardial contractility. The drug exists as a mixture of stereoisomers that contribute to both actions.

Administration is oral for chronic hypertension and intravenously for rapid blood pressure control in emergencies. Oral labetalol is typically started at a low dose and titrated to achieve target blood pressure; IV dosing is given in boluses or infusions with careful monitoring of heart rate and blood pressure. Onset of IV effect is usually within minutes; the duration lasts several hours.

Clinical uses include chronic hypertension, hypertensive crisis, and pregnancy-related hypertension, including preeclampsia and eclampsia, where rapid blood pressure reduction is desired without excessive decreases in placental perfusion.

Contraindications include asthma or other bronchospastic airway disease (due to beta-2 blockade), significant bradycardia, higher-degree heart block, compensated or decompensated heart failure, cardiogenic shock, and hypersensitivity. Caution is advised in patients with diabetes, peripheral vascular disease, or those taking other antihypertensives.

Common adverse effects are dizziness, fatigue, orthostatic hypotension, bradycardia, and nausea; bronchospasm may occur in susceptible individuals. Labetalol can mask signs of hypoglycemia and may interact with other antihypertensives, calcium channel blockers, and insulin therapy, requiring careful monitoring during combination treatment.