Labetalol
Trandate
Combined alpha-1 + non-selective beta antagonist (β:α ratio ~7:1 IV)
Combined alpha-1 + beta-1 + beta-2 antagonist. Alpha-1 blockade → vasodilation; beta blockade → reduces HR + contractility + reflex tachycardia from alpha blockade. Gives smooth BP reduction without reflex tachycardia (both alpha + beta covered) — a double-acting agent.
Indications
- •Acute hypertension perioperative (bolus or infusion)
- •Hypertensive emergency
- •Aortic dissection (with esmolol for HR control first)
- •Pheochromocytoma intraop crisis (after alpha blockade)
- •Pregnancy HTN (preeclampsia — first-line antihypertensive in OB)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Acute HTN bolus | 5-20 mg IV slow over 2 min, repeat q10 min, max 300 mg/24 h | — |
| Continuous infusion | 0.5-2 mg/min IV titrated, max 300 mg total | — |
| Pregnancy HTN | 10-20 mg IV q10-15 min PRN, or 1-2 mg/min infusion | — |
Pharmacokinetics
Onset 5-10 min IV. Peak 5-15 min. Duration 2-6 h (much longer than esmolol). Hepatic glucuronidation, renal excretion (5% unchanged). Crosses placenta but minimal fetal effect — preferred OB antihypertensive.
Hemodynamic effects
↓HR (modest), ↓SVR, ↓BP. Beta-blockade prevents reflex tachycardia from alpha-blockade. Maintains cardiac output (minimal direct negative inotropy).
Side effects
- !Bradycardia (additive with other beta-blockers)
- !Bronchospasm (less than non-selective due to combined mechanism but still risk)
- !Heart block (especially in AV node disease)
- !Hepatocellular injury rare with chronic use
- !Decompensation in heart failure
Contraindications
- ×Severe bradycardia, sick sinus syndrome
- ×Heart block 2nd/3rd degree
- ×Cardiogenic shock, decompensated heart failure
- ×Severe asthma (relative)
- ×Pheochromocytoma WITHOUT prior alpha blockade
Clinical pearls
- ★PREGNANCY first-line antihypertensive (preeclampsia) — preferred over hydralazine in many centers (smoother control, less tachycardia, less crystalloid loading needed).
- ★Postop HTN in PACU: 5-10 mg IV bolus is rapid + effective; longer duration than esmolol means less re-dosing.
- ★Bridging from esmolol to oral/longer-acting: labetalol IV → labetalol PO transition.
- ★Aortic dissection: combine with esmolol — esmolol controls HR first (beta-blockade limits reflex tachycardia), then labetalol or nicardipine for additional BP control.
- ★Pheochromocytoma + acute hypertensive crisis: ONLY after adequate alpha blockade (phenoxybenzamine ≥7 days) — labetalol's beta-blockade in unblocked patient produces unopposed alpha + lethal bradycardia.
Education only — confirm against current package inserts and institutional protocols. Doses assume normal organ function unless otherwise noted.