Labetalol
Oral 200 mg or IV 20 mg (then 40–80 mg) for severe hypertension in pregnancy; IV infusion for hypertensive emergencies.
On this page
Dose
| Situation | Dose |
|---|---|
| Severe hypertension in pregnancy (oral) | 200 mg, repeat after 1 hour if needed |
| IV bolus | 20 mg over 2 minutes, then 40–80 mg every 10 minutes, max 300 mg |
| IV infusion | 20–160 mg/hour, titrated (HDU) |
| Maintenance in pregnancy | 100–400 mg 2–3 times daily |
How it works
Labetalol blocks beta-1 and beta-2 receptors and, to a lesser extent, alpha-1 receptors. Blocking alpha-1 dilates arterioles and lowers peripheral resistance; blocking beta-1 prevents the reflex rise in heart rate and cardiac output that a pure vasodilator would cause. BP therefore falls smoothly without tachycardia, and cerebral and placental blood flow are reasonably preserved. IV labetalol acts within about 5 minutes; oral doses take 1 to 2 hours.
When it is used
- First-line treatment of hypertension in pregnancy, including chronic hypertension, gestational hypertension and pre-eclampsia (NICE).
- Severe hypertension in pregnancy (160/110 mmHg or above): oral if the woman can swallow and is not in crisis, IV if BP is very high or oral treatment fails.
- Hypertensive emergency with end-organ damage, under monitoring, aiming for a controlled reduction.
- Aortic dissection, to reduce heart rate and BP (often by infusion).
- Some neurological emergencies, such as BP control before stroke thrombolysis.
It is not for:
- Hypertensive urgency without organ damage, which needs gradual oral treatment rather than IV boluses.
- Patients with asthma, where nifedipine or hydralazine are alternatives in pregnancy.
- Cocaine- or amphetamine-related hypertension (as a first drug; benzodiazepines are used first).
Cautions
- Avoid in asthma, heart block, severe bradycardia, acute heart failure.
Contraindications
- Asthma or a history of bronchospasm.
- Second- or third-degree heart block, sick sinus syndrome, HR below about 50 to 60.
- Cardiogenic shock, uncontrolled heart failure.
- Phaeochromocytoma unless alpha-blockade is already established (specialist).
Side effects
- Postural hypotension: keep the patient lying down during and for 3 hours after IV doses.
- Bradycardia, tiredness, headache, scalp tingling, nasal congestion.
- Bronchospasm in susceptible patients.
- Rare but serious liver injury (usually reversible); stop if LFTs rise or jaundice appears.
- Neonatal bradycardia and low glucose when used near delivery.
Interactions
- Verapamil and diltiazem: risk of heart block and severe bradycardia.
- Other antihypertensives and anaesthetic agents: additive fall in BP.
- Insulin and sulfonylureas: beta-blockade can mask the warning signs of hypoglycaemia.
Monitoring
- During IV treatment: BP and HR every 5 to 15 minutes until stable, then every 30 minutes. Many units use an HDU setting.
- Target in pregnancy: BP 135/85 mmHg or below (NICE). Avoid dropping BP too fast; check fetal heart rate (CTG) when IV agents are used.
- In pre-eclampsia, also monitor urine output, platelets, creatinine, LFTs and reflexes. Watch for the need for magnesium sulfate.
- In hypertensive emergency, aim to lower mean BP by no more than about 25% in the first hour unless there is aortic dissection.
Pregnancy and breastfeeding
Labetalol is the first choice for hypertension in pregnancy. The baby should be observed after birth for bradycardia and low blood glucose, and neonatal glucose monitored per local protocol. It is compatible with breastfeeding.
Practical tips
- Oral labetalol is taken with food.
- IV labetalol (5 mg/mL) can be given undiluted as a slow bolus; for infusion, it is commonly diluted to 1 mg/mL in 5% glucose or 0.9% sodium chloride.
- Check that the patient is not asthmatic before the first dose, and write it clearly if there is any history of wheeze.
- Record pulse with every BP; withhold doses and tell your senior if HR falls below about 60.
- When switching from IV to oral, start oral treatment before stopping the infusion so BP does not rebound.
Severe BP in pregnancy is an emergency for both mother and baby. Treat to protect against stroke, but check reflexes, urine protein and symptoms of eclampsia at the same time.
See Pre-eclampsia and eclampsia, Hypertensive emergency and High blood pressure on the ward. For exam background, read Antihypertensives in pregnancy and Adrenergic drugs.
Frequently asked questions
Is labetalol safe in pregnancy?
Yes, it is first-line for high BP in pregnancy.
What is the alternative to labetalol in asthma?
Oral nifedipine (modified-release) or IV hydralazine are used for severe hypertension in pregnancy when labetalol is contraindicated.
How quickly does IV labetalol work?
Within about 5 minutes, with a peak at around 5 to 15 minutes. That is why repeat boluses are spaced about 10 minutes apart.
Can labetalol be continued while breastfeeding?
Yes. Only small amounts pass into breast milk, and it is widely used after delivery.
Used in these guides
Sources
Doses on this page are typical doses from the sources above. Always confirm with a current drug reference, the product leaflet and your hospital protocol, especially in children, pregnancy and kidney or liver disease.
For FCPS Part 1
Revising for FCPS Part 1? Labetalol is covered in our textbook chapter Antihypertensives in pregnancy, with practice MCQs.