Labetalol Hydrochloride (Normodyne, Trandate)

Anesthesia Implications

Classification: Beta-Blocker
Therapeutic Effects: Antihypertensive
Time to Onset: IV: 2-5 min
Time to Peak: IV: 5-15 minutes
Duration: 2-4 hrs

Contraindications

Bronchial Asthma
Overt cardiac failure
2nd and 3rd degree heart blocks
Cardiogenic shock
Severe bradycardia

Primary Considerations

Heart rate – Labetalol administration does NOT drastically reduce heart rate or result in reflex tachycardia.

Blood pressure – Labetalol will produce a dose-dependent decrease in blood pressure. Cerebral blood flow and ICP should remain unaffected.

Bronchoconstriction – Labetalol blocks B2 adrenergic receptors, which could contribute to bronchospasm in susceptible patients. As a beta blocker, labetalol will increase resistance to beta agonists (eg albuterol), so be careful with the respiratory patients!

Drug interactions – Labetalol will supress/blunt reflex tachycardia seen with administration of nitroglycerin. Hypotensive affects of volatile anesthetics, opoids, etc will be potentiated by labetalol. Cimetidine will increase labetalol bioavailability.

OB – Neonatal hypoglycemia and bradycardia risk is increased when the mother is given labetalol at the time of delivery

IV push dose

2.5 – 20 mg. Slow push over 2 minutes

IV infusion dose

0.5 – 2.0 mg/min. MAX: cumulative dose of 1-4 mg/kg
Typically prepared by adding 200 mg of labetalol in 200 ml of normal saline or D5W for a concentration of 1 mg/ml

Method of Action

Labetalol is a selective, competitive, and alpha 1-adrenergic antagonist. In addition, labetalol is a non-selective, competitive, beta-adrenergic (B1 and B2) blocker. The ratio is 1:7 alpha to beta blockade.

Metabolism

Hepatic, urinary, fecal