Labetalol

Aka: Labetalol, Trandate

1. See Also
   1. Beta Blocker
   2. Alpha Adrenergic Antagonist
   3. Carvedilol
2. Indications
   1. Refractory Hypertension
      1. Effective outpatient agent in oral form patients with Refractory Hypertension
   2. Hypertensive Emergency
      1. Nicardipine has replaced intravenous Labetalol for Hypertensive Emergency
         1. Labetalol is difficult to achieve Blood Pressure control in Hypertensive Crisis despite titration
         2. Labetalol is short acting
      2. Labetalol is a preferred agent when compared with Hydaralazine and Clonidine
3. Contraindications
   1. Asthma
   2. Bradycardia
4. Pharmacokinetics
   1. Well absorbed and high first-pass metabolism (liver metabolism)
5. Mechanism
   1. Combination of classes (similar to Carvedilol)
      1. Lowers Blood Pressure without reflex Tachycardia
      2. Nonselective Beta Blocker (7 fold more beta than alpha activity)
         1. Binds vascular (and Bronchial) Smooth Muscle beta receptors
         2. Decreases Heart Rate, Cardiac Output and Blood Pressure
      3. Selective Alpha-1 Adrenergic Antagonist (weak compared with beta activity)
         1. Competitively binds vascular Smooth Muscle alpha-1 Adrenergic Receptors
         2. Blocks peripheral blood vessel Vasoconstriction
   2. Primary activity is as a negative inotrope
      1. Chronotropic effect is mild
6. Dosing: Adults
   1. Adjust dose in liver and renal Impairment
   2. Oral
      1. Start: 100 mg orally twice daily
      2. Target: 200 to 600 mg orally twice daily
      3. Maximum: 2400 mg/day
   3. Intravenous Injection
      1. Start: 20 mg slow IV injection
      2. Next: 40-80 mg every 10 minutes as needed
      3. Cummulative Maximum: 200-300 mg
   4. Intravenous Infusion
      1. Start 0.5 to 2 mg/min IV up to cummulative maximum of 200-300 mg
7. Dosing: Children (Not FDA approved)
   1. Oral
      1. Start: 4 mg/kg/day orally divided twice daily
      2. Maximum: 40 mg/kg/day up to adult maximum of 2400 mg
   2. Intravenous Infusion
      1. Dose: 0.3 to 1 mg/kg/dose up to 20 mg slow IV injection up to every 10 minutes
      2. Cummulative Maximum: 200-300 mg
   3. Intravenous Infusion
      1. Start 0.4 to 1 mg/kg/hour IV up to 3 mg/kg/hour
8. Adverse Effects
   1. May worsen acute exacerbations of Congestive Heart Failure
   2. Fatigue
   3. Erectile Dysfunction
   4. Orthostatic Hypotension
9. Drug Interactions
   1. Systemic Beta Agonists
      1. Labetalol blocks bronchodilation
10. References
    1. Olson (2020) Clinical Pharmacology, MedMaster, Miami, p. 66
    2. Hamilton (2020) Tarascon Pocket Pharmacopeia, Jones and Bartlett, accessed on IOS, 4/9/2021