Ephedrine

Mechanism of Action 1

  • Ephedrine is a sympathomimetic with both indirect and direct effects on catecholamine receptors:
    • Indirect: promotes the release of endogenous norepinephrine which acts on alpha and beta receptors
    • Direct: partial activity on alpha and beta receptors contributes to its activity
  • Overall, a bolus of ephedrine will raise the blood pressure, heart rate, and cardiac output of a patient. It is less potent than other vasopressors but acts slightly longer

Indications 1

  • Hypotension in anesthesia: Used for treatment of intraoperative hypotension, especially when caused by spinal or epidural anesthesia.
  • Nasal decongestion: Historically used as a decongestant.

Dosage 1

  • Hypotension Management (IV):
    • Adults: 5-10 mg IV bolus, may repeat every 3-5 minutes as needed.
    • Pediatrics: 0.1 mg/kg IV, may repeat as needed.
  • Intramuscular: 25-50 mg for mild hypotension

Complications 1

  • Tachycardia: Due to β1 receptor stimulation.
  • Hypertension: Prolonged use or high doses may lead to excessive vasoconstriction.
  • Tolerance: Repeated doses may lead to tachyphylaxis (decreased response).

Pharmacokinetics 1

  • Onset of Action: Rapid, typically within minutes when administered IV.
  • Duration: Short, lasting about 10-15 minutes IV.
  • Metabolism: Partially hepatic, with some unmetabolized drug excreted unchanged in the urine.
  • Elimination Half-life: Approximately 3-6 hours.

References

  1. Shafer SL, Rathmell JP, Flood P. Stoelting’s Pharmacology and Physiology in Anesthetic Practice. Fifth edition. Philadelphia: Wolters Kluwer Health, 2015. ↩ ↩2 ↩3 ↩4 ↩5