Molecule

Drug Groups

approved

Description

Blocker of both alpha- and beta-adrenergic receptors that is used as an antihypertensive. [PubChem]

Indication

For the management of hypertension (alone or in combination with other classes of antihypertensive agents), as well as chronic stable angina pectoris and sympathetic overactivity syndrome associated with severe tetanus. Labetalol is used parenterally for immediate reduction in blood pressure in severe hypertension or in hypertensive crises when considered an emergency, for the control of blood pressure in patients with pheochromocytoma and pregnant women with preeclampsia, and to produce controlled hypotension during anesthesia to reduce bleeding resulting from surgical procedures.

Pharmacology

Labetalol is an selective alpha-1 and non-selective beta adrenergic blocker used to treat high blood pressure. It works by blocking these adrenergic receptors, which slows sinus heart rate, decreases peripheral vascular resistance, and decreases cardiac output. Labetalol has two asymmetric centers and therefore, exists as a molecular complex of two diastereoisomeric pairs. Dilevalol, the R,R' stereoisomer, makes up 25% of racemic labetalol.

Toxicity

LD₅₀ = 66 mg/kg (Rat, IV). Side effects or adverse reactions include dizziness when standing up, very low blood pressure, severely slow heartbeat, weakness, diminished sexual function, fatigue

Affected Organisms

Biotransformation

Primarily hepatic, undergoes significant first pass metabolism

Absorption

Completely absorbed (100%) from the gastrointestinal tract with peak plasma levels occurring 1 to 2 hours after oral administration. The absolute bioavailability of labetalol is increased when administered with food.

Half Life

6-8 hours

Protein Binding

50%

Elimination

These metabolites are present in plasma and are excreted in the urine, and via the bile, into the feces.

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