LABETALOL

Beta adrenoceptor blocker with arteriolar vasodilatory action. It lowers peripheral resistance, slows the heart rate and depresses the myocardium

Dosage Forms

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Injection

5 mg/ml

Uses

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  • Severe hypertension including hypertension in pregnancy
  • Hypertension following myocardial infarction
  • Hypertensive crisis

Dose and Duration

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Hypertension of pregnancy
Adult: by IV injection, 20 mg/hour, doubled every 30 minutes (usual max 160 mg/hour)
Hypertension following myocardial infarction
Adult: by IV injection, 15 mg/hour gradually increased to maximum dose of 120 mg/hour
Hypertension
Adult and child over 12 years: by IV injection, 50 mg over at least 1 minute, repeated after 5 minutes if necessary (max total dose 200 mg) By IV infusion: 2 mg/minute until satisfactory response, then discontinue (usual total dose 50–200 mg)
Child 1 month–12 years: by IV injection, 0.25–0.5 mg/kg as a single dose (max 20 mg)
Hypertensive emergencies
Child 12–18 years: by IV infusion over at least 1 minute, 30–120 mg/hour adjusted at 15 minute intervals according to response
Child 1 month–12 years: by IV infusion, initially 0.5–1 mg/kg/hour adjusted at intervals of at least 15 minutes according to response (max 3 mg/kg/hour)
Neonate: by IV infusion, 0.5 mg/kg/hour adjusted at intervals of at least 15 minutes according to response (max 4 mg/kg/hour)

Contraindications

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  • Cardiogenic shock
  • Uncontrolled, early or digitalis refractory heart failure
  • Sick sinus syndrome
  • 2nd or 3rd degree heart block
  • Prinzmetal's angina
  • History of wheezing or asthma
  • Untreated pheochromocytoma
  • Metabolic acidosis
  • Bradycardia
  • Hypotension
  • Hypersensitivity to labetalol
  • Severe peripheral circulatory disturbances
  • Where peripheral vasoconstriction suggests low cardiac output in hypertension following infarction

Side Effects

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  • Postural hypotension
  • Tiredness, weakness, headache
  • Rashes, scalp tingling
  • Difficulty in urination
  • Epigastric pain, nausea, vomiting
  • Liver damage

Interactions

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  • Prazosin, tamsulosin, alfuzosin (enhanced hypotensive effect)
  • Amiodarone, flecainide (increased risk of AV block, myocardial depression, bradycardia)
  • Nifedipine (risk of severe hypotension and heart failure)
  • Diltiazem (increased risk of AV block and bradycardia)
  • Verapamil (asystole, severe hypotension, heart failure)
  • Clonidine (increased risk of withdrawal hypertension)
  • Epinephrine, dobutamine (increased risk of severe hypertension and bradycardia)

Patient Instructions

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  • Avoid standing or sitting upright during and 3 hours after intravenous administration

Pregnancy

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  • Do not use (except in emergency)

Breast-feeding

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  • Do not use

⚠️ Caution

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  • Reduce dose in renal and hepatic impairment
  • Risk of severe hepatic damage after both short- and long-term treatment. At first confirmation of liver damage, withdraw labetalol immediately and do not restart it
  • Use with caution in patients with peripheral circulatory disorders, history of psoriasis
  • Patients with ischaemic heart disease should not discontinue labetalol abruptly
  • Monitor heart rate after injection or infusion, in case of severe bradycardia, control it using 1–2 mg of IV atropine
  • Avoid use in 1st trimester of pregnancy. Labetalol crosses placental barrier and may cause alpha and beta adrenoceptor blockade in the neonate, which may develop up to 2 days after birth. Labetalol is excreted in breast milk