The Sound of Evolution
Labetalol
Mechanism of action:
Labetalol is an α- and β-adrenergic receptor blocker with predominant β-blocking activity and secondary α₁-blocking activity. It blocks β₁ receptors in the cardiovascular system, reducing heart rate and myocardial contractility and thereby lowering cardiac output. It also blocks β₂ receptors, reducing sympathetic-mediated vasodilation and bronchodilation, although this effect is relatively less prominent with labetalol. In addition, labetalol blocks α₁ receptors, inhibiting vascular smooth muscle contraction, causing peripheral vasodilation, reducing systemic vascular resistance, and lowering blood pressure.
Reference(s):
1. Yeleswaram K et al. (1993). Disposition, metabolism, and pharmacodynamics of labetalol in adult sheep. Drug Metab Dispos.
2. McNeil JJ et al. (1984). Clinical pharmacokinetics of labetalol. Clin Pharmacokinet.
3. Opie LH et al. (1988). Role of vasodilation in the antihypertensive and antianginal effects of labetalol: implications for therapy of combined hypertension and angina. Cardiovasc Drugs Ther.