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Pharmacology · Beta blockers

Labetalol !

A combined α1 and β blocker, by mouth or IV. Used for severe hypertension and is a first choice for high blood pressure in pregnancy.

Updated 2026-11-01

  • Class: Beta blockers
  • Receptor: β- and α1-adrenergic receptors
  • ATC code: C07AG01

The figure shows carvedilol, another combined α1 and β blocker, in the human β2 receptor; no structure with labetalol bound is available.

Target in 3D: β- and α1-adrenergic receptors. PDB structure 6PS3 (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Labetalol blocks α1 receptors selectively and β1 and β2 receptors without selectivity, with stronger β than α block. α1 block dilates arterioles; β block prevents the reflex tachycardia that vasodilation would cause. Blood pressure falls with little change in heart rate and cardiac output, and falls more when standing than lying down.

  1. Labetalol blocks α1 receptors and β1/β2 receptors
  2. α1 block dilates arterioles and lowers resistance
  3. β block prevents reflex tachycardia

Pharmacokinetics

Absorption
Large first-pass effect by mouth; liver disease raises its bioavailability
Metabolism
Liver, mainly by conjugation
Half-life
About 6 to 8 hours by mouth

Indications

Adverse effects

Common

  • Orthostatic hypotension and dizziness
  • Tingling of the scalp
  • Nausea
  • Fatigue

Contraindications

  • Bronchial asthma or obstructive airway disease
  • Overt heart failure or cardiogenic shock
  • Heart block greater than first degree or severe bradycardia
  • Conditions with severe and prolonged hypotension

Key interactions

Inhaled anaesthetics such as halothane
Added lowering of blood pressure
β2 agonist bronchodilators
Labetalol blunts their bronchodilator effect
Cimetidine
Higher bioavailability of oral labetalol

What is monitored

  • Blood pressure and heart rate, lying and standing
  • Continuous monitoring during IV use
  • Liver tests if symptoms of liver injury appear
  • Fetal heart rate in pregnancy

Administration and safety

  • IV doses are given with the patient lying down and continuous blood pressure monitoring
  • After IV doses, the patient does not get up unassisted until standing blood pressure is checked
  • Many «-olol» names look alike: the name and route are checked

Nursing care

  • Measure blood pressure often during IV dosing and report a sharp drop or bradycardia
  • Help the patient up the first times; watch for orthostatic symptoms
  • Ask about wheezing; teach the patient to report dark urine, jaundice or itching
  • In pregnancy, monitor the mother's blood pressure and the fetal heart rate

Pregnancy and breastfeeding

One of the preferred antihypertensives in pregnancy; low blood pressure, slow heart rate, low glucose and breathing depression have been reported in babies exposed before birth, so the newborn is watched.

Test yourself

Think of the answer, then tap the question to see it.

Which receptors does labetalol block?

α1 receptors selectively plus β1 and β2 receptors, with stronger β block.

Why does labetalol not cause reflex tachycardia like a pure vasodilator?

Its β block stops the heart from speeding up in response to the vasodilation from α1 block.

Why is the patient kept lying down during IV labetalol?

Blood pressure falls more when standing, so standing up can cause marked orthostatic hypotension.

Which antihypertensives are used in pregnancy, and which are contraindicated?

Used: labetalol and nifedipine (also methyldopa). Contraindicated: ACE inhibitors and ARBs.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - LABETALOL HYDROCHLORIDE injection, solution (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 32 (McGraw Hill, 2023).

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Representative model, for educational purposes only.