Racemic Epinephrine (nebulized)
Asthmanefrin · S2
Inhaled non-selective adrenergic agonist (50:50 D + L isomers)
Topical airway α-agonism → mucosal vasoconstriction → reduced edema. β2 effect contributes to bronchodilation. Used to treat upper-airway edema rather than lower-airway bronchospasm.
Indications
- •Post-extubation stridor
- •Croup (laryngotracheobronchitis)
- •Postoperative airway edema after head-and-neck or thyroid surgery
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Adult / pediatric post-extubation or croup | 0.5 mL of 2.25% solution in 3 mL NS by nebulizer; repeat q20 min × 2 if needed | 0.05 mL/kg of 2.25% solution (max 0.5 mL) in 3 mL NS |
Pharmacokinetics
Onset 10 min nebulized. Duration 2 h. Minimal systemic absorption from airway.
Hemodynamic effects
Minimal at appropriate nebulized dose; tachycardia possible at high cumulative dose.
Respiratory effects
Reduces airway edema; can mask the underlying cause and rebound when the drug wears off.
Side effects
- !Tachycardia, palpitations
- !Tremor (β2)
- !Hypertension at high dose
- !REBOUND EDEMA — the airway can re-swell at 2 h as drug wears off
Contraindications
- ×Hypersensitivity
Clinical pearls
- ★OBSERVE 4 HOURS POST-DOSE: rebound edema is the big trap. Patients who get racemic epi for post-extubation stridor need a 4-hour observation period before discharge or extubation re-trial.
- ★CUFF-LEAK TEST AS PREDICTOR: positive cuff-leak (volume <110 mL or 12% of TV) predicts post-extubation stridor. Pretreat with methylprednisolone 20 mg q4 h × 4 doses (Cheng et al, Crit Care 2006).
- ★STANDARD EPI OK: racemic was historically thought safer (D-isomer is inactive); modern data show standard L-epinephrine 1 mg in 5 mL NS works equally well at the same airway dose. Use whatever's available.
- ★CROUP DOSING: pediatric dose is weight-based but typically 0.5 mL of 2.25% in 3 mL NS for any child >5 kg. Watch the same 4-hour rebound window.
Other drugs in Aerosols / Inhalers
- Albuterol
Selective β2 agonist → activates Gs → ↑cAMP → bronchial smooth-muscle relaxation. Some β1 cross-reactivity at high doses (tachycardia).
- Ipratropium
Inhaled quaternary ammonium muscarinic antagonist — minimal systemic absorption. Blocks parasympathetic vagal tone in airways → bronchodilation. Synergistic with β2 agonists.
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