Recommended Starting Dose for Labetalol Infusion
For continuous IV labetalol infusion, the recommended starting dose is 2 mg/min, which is prepared by adding 200 mg of labetalol to 160 mL of IV fluid (creating a 1 mg/mL solution) and infusing at 2 mL/min. 1
Preparation Methods for Continuous Infusion
There are two standard methods for preparing labetalol infusion:
Method 1: Add 200 mg labetalol (two 20-mL vials or one 40-mL vial) to 160 mL of compatible IV fluid to create a 1 mg/mL solution. Administer at 2 mL/min to deliver 2 mg/min. 1
Method 2: Add 200 mg labetalol (two 20-mL vials or one 40-mL vial) to 250 mL of compatible IV fluid to create a 2 mg/3 mL solution. Administer at 3 mL/min to deliver approximately 2 mg/min. 1
Dosing Considerations
- The rate of infusion should be adjusted according to blood pressure response. 1
- The effective IV dose usually ranges from 50-200 mg total. 1
- A total dose of up to 300 mg may be required in some patients. 1
- The maximum cumulative dose is typically 300 mg in 24 hours, though higher doses have been used in specific clinical scenarios. 2
Clinical Scenario-Specific Dosing
For Hypertensive Emergencies:
- Initial dose: 0.3-1.0 mg/kg (maximum 20 mg) by slow IV injection every 10 minutes, with a maximum cumulative dose of 300 mg. 3
- For continuous infusion, start at 2 mg/min as described above. 1
For Ischemic Stroke Patients:
- Not eligible for thrombolytic therapy: 10-20 mg IV over 1-2 minutes, may repeat or double every 10 minutes (maximum 300 mg). 4
- Eligible for thrombolytic therapy: 10-20 mg IV over 1-2 minutes, may repeat once pre-treatment. During/after treatment, 10 mg IV over 1-2 minutes may be repeated every 10-20 minutes (maximum 300 mg). 4, 3
Monitoring and Safety Considerations
- Blood pressure should be monitored during and after completion of the infusion. 1
- Avoid rapid or excessive falls in either systolic or diastolic blood pressure. 1
- Patients should remain supine during administration, as substantial falls in blood pressure on standing should be expected. 1
- The maximum effect usually occurs within 5 minutes of each bolus injection. 1
Contraindications
- Reactive airways disease or chronic obstructive pulmonary disease 4, 3
- Second or third-degree heart block or bradycardia 4, 3
- Decompensated heart failure 4, 3
Important Caveats
- Labetalol is particularly useful in hyperadrenergic states. 4, 3
- For prolonged administration, be prepared for potential cardiovascular depression with rescue medications available (glucagon, beta-agonists, phosphodiesterase inhibitors, insulin, and vasopressin). 5
- The half-life of labetalol is 5-8 hours, so steady-state blood levels will not be reached during typical infusion periods. 1