Labetalol is used in hypertensive emergencies in pregnancy primarily because it:
- A Blocks both alpha-1 and beta receptors (1:3 ratio oral; 1:7 IV), lowering BP without reflex tachycardia ✓
- B Selectively blocks beta-1 receptors, reducing heart rate without affecting peripheral resistance
- C Acts as a direct vasodilator by releasing nitric oxide from vascular endothelium
- D Inhibits renin release and reduces angiotensin II-mediated vasoconstriction
Correct answer: A. Blocks both alpha-1 and beta receptors (1:3 ratio oral; 1:7 IV), lowering BP without reflex tachycardia
Explanation
Labetalol is a combined alpha-1 and non-selective beta-blocker. Its alpha-1 blockade reduces peripheral vascular resistance (lowering BP) while beta-blockade prevents the reflex tachycardia that pure vasodilators cause. The oral alpha:beta blocking ratio is approximately 1:3 and the IV ratio is 1:7. It is safe in pregnancy and does not cause fetal bradycardia at therapeutic doses.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.