What is the recommended dose of labetalol (alpha/beta adrenergic blocker) for treating severe hypertension?

Recommended Dosage of Labetalol for Severe Hypertension

For severe hypertension, labetalol should be administered intravenously with an initial dose of 20 mg (0.25 mg/kg) by slow IV injection over 2 minutes, followed by additional doses of 40-80 mg at 10-minute intervals until desired blood pressure is achieved or a maximum total dose of 300 mg is reached. 1

Intravenous Administration Methods

Method 1: Repeated IV Injections

• Initial dose: 20 mg (0.25 mg/kg) administered by slow IV injection over 2 minutes 1
• Blood pressure should be measured immediately before injection and at 5 and 10 minutes after injection to evaluate response 1
• Additional injections of 40 mg or 80 mg can be given at 10-minute intervals until desired blood pressure is achieved or a total of 300 mg has been administered 1
• Maximum effect usually occurs within 5 minutes of each injection 1

Method 2: Slow Continuous Infusion

• Dilute 200 mg labetalol (two 20-mL vials or one 40-mL vial) in 160 mL of IV fluid to create a 1 mg/mL solution 1
• Administer at a rate of 2 mL/min to deliver 2 mg/min 1
• Alternatively, dilute 200 mg labetalol in 250 mL of IV fluid (approximately 2 mg/3 mL) and administer at 3 mL/min 1
• The effective IV dose is usually in the range of 50 to 200 mg, with a total dose of up to 300 mg sometimes required 1

Dosing for Specific Hypertensive Emergencies

• Malignant hypertension: Labetalol is first-line therapy with a goal of reducing mean arterial pressure by 20-25% over several hours 2
• Hypertensive encephalopathy: Labetalol is first-line therapy with immediate blood pressure reduction targeting 20-25% decrease in mean arterial pressure 2
• Acute ischemic stroke:
  • For BP >220 mmHg systolic or >120 mmHg diastolic: Labetalol 10-20 mg IV over 1-2 minutes, with goal of 15% reduction in MAP 2, 3
  • For patients eligible for thrombolytic therapy with BP >185/110 mmHg: Labetalol 10-20 mg IV over 1-2 minutes 3
• Acute hemorrhagic stroke: Labetalol is first-line for immediate reduction of systolic BP to 130-180 mmHg 2
• Severe pre-eclampsia/eclampsia: Labetalol is first-line therapy with a target systolic BP <160 mmHg and diastolic BP <105 mmHg 2

Blood Pressure Monitoring

• Blood pressure should be monitored during and after completion of infusion or IV injections 1
• Avoid rapid or excessive falls in either systolic or diastolic blood pressure 1
• In patients with excessive systolic hypertension, the decrease in systolic pressure should be used as an indicator of effectiveness in addition to diastolic response 1

Special Considerations and Contraindications

• Labetalol is particularly useful in hypertensive emergencies with hyperadrenergic states 3
• Contraindicated in patients with:
  • Reactive airways disease or chronic obstructive pulmonary disease 3
  • Second or third-degree heart block 2, 3
  • Bradycardia 2, 3
  • Decompensated heart failure 2, 3
• Labetalol may be preferred in hypertensive encephalopathy as it leaves cerebral blood flow relatively intact compared to nitroprusside 2
• Safety concerns with prolonged high-dose infusions include profound cardiovascular compromise requiring intervention with glucagon, beta-agonists, or vasopressors 4

Transition to Oral Therapy

• Oral labetalol should begin when supine diastolic blood pressure has begun to rise 1
• Recommended initial oral dose is 200 mg, followed in 6-12 hours by an additional dose of 200-400 mg depending on blood pressure response 1
• Subsequent inpatient titration may proceed from 400 mg/day (200 mg twice daily) up to a maximum of 2400 mg/day (1200 mg twice daily) 1