Ephedrine

(generic)

Indirect + direct mixed alpha + beta sympathomimetic

Indirect-acting sympathomimetic — promotes release of stored norepinephrine from presynaptic vesicles AND has direct alpha + beta receptor agonism. Mixed action → increases HR (β1) + contractility (β1) + SVR (α1). Tachyphylaxis develops with repeated dosing (depleted NE stores).

Indications

•Hypotension during anesthesia, especially with bradycardia (treats both HR + BP)
•Hypotension after spinal/epidural anesthesia (alternative to phenylephrine, especially in non-OB)
•Symptomatic hypotension in cardiac surgery (vasoconstrictor + inotropic support)

Dosing

Context	Adult	Pediatric
Hypotension bolus	5–10 mg IV; can repeat q3–5 min (max ~50 mg/session before tachyphylaxis)	0.1–0.2 mg/kg IV; can repeat q3–5 min
IM bolus (no IV)	25–50 mg IM	0.5 mg/kg IM

Pharmacokinetics

Onset 1-2 min IV. Duration 10-15 min. Renal excretion (~95% unchanged). Half-life 3-6 h. Crosses placenta (use during cesarean — historical concern about fetal acidemia at high doses, but practically OK at standard doses).

Hemodynamic effects

↑HR, ↑contractility, ↑SVR → ↑BP. Useful for hypotension + bradycardia (in contrast to phenylephrine which is pure alpha → may cause reflex bradycardia).

Side effects

!Tachycardia (problematic in CAD, AS)
!Tachyphylaxis (depletion of stored norepinephrine)
!Hypertension overshoot if dosed too aggressively
!Catecholamine-like effects: tremor, anxiety in awake patient
!Possible MI in susceptible patients (catecholamine-driven)

Contraindications

×Tachyarrhythmia
×Severe HTN, pheochromocytoma (uncontrolled catecholamine surge)
×Concurrent MAOI use (severe HTN crisis)

Clinical pearls

★FIRST-LINE for hypotension WITH BRADYCARDIA in non-OB cases — treats both HR + BP. If hypotension WITHOUT bradycardia or with tachycardia, phenylephrine is preferred.
★Cesarean spinal hypotension: PHENYLEPHRINE infusion is preferred over ephedrine boluses (Ngan Kee Anesth Analg 2010 — less fetal acidemia). Ephedrine has fallen from first-line in OB.
★TACHYPHYLAXIS: after 3-4 boluses, switch to phenylephrine or norepinephrine (works on different mechanism — direct receptor agonism unaffected by NE depletion).
★MAOI patients: indirect-acting sympathomimetics → catecholamine SURGE (norepinephrine pool not metabolized normally) → severe HTN crisis. Use direct-acting (phenylephrine, norepinephrine) instead.
★Standard concentration: 50 mg/mL ampoule; dilute to 5 mg/mL in saline (1 mL bolus) for routine intraop use.