First-Line Injection for Anaphylaxis
Intramuscular epinephrine is the only first-line treatment for anaphylaxis and must be administered immediately—there are no acceptable alternatives or substitutes. 1, 2
Immediate Administration Protocol
Inject epinephrine 0.01 mg/kg of 1:1000 concentration (1 mg/mL) intramuscularly into the anterolateral thigh (vastus lateralis muscle) as soon as anaphylaxis is recognized. 1, 2, 3
Specific Dosing by Weight
- Adults and children ≥50 kg: 0.5 mg (maximum dose) 1, 3
- Children and teenagers 25-50 kg: 0.3 mg (maximum dose) 1, 3
- Children 10-25 kg: 0.15 mg 1, 4
- Infants 7.5-15 kg: 0.15 mg (or 0.1 mg with newer formulations) 1
Route and Technique
The intramuscular route in the lateral thigh is vastly superior to subcutaneous injection, achieving peak plasma concentrations in 8±2 minutes compared to 34±14 minutes with subcutaneous administration. 5, 2, 4 This rapid absorption is critical for reversing life-threatening hypotension and airway obstruction. 5
Insert the needle at a 90-degree angle perpendicular to the skin surface in the mid-outer aspect of the anterolateral thigh. 4 The injection can be administered through clothing if necessary during emergencies, as any delay in administration is associated with increased mortality. 4
Repeat Dosing
Repeat the same dose every 5-15 minutes if symptoms persist or do not adequately respond. 1, 4, 3 Approximately 7-18% of patients require more than one dose, and these individuals are at higher risk for hospital admission and biphasic reactions. 1
Critical Evidence Hierarchy
The American Academy of Allergy, Asthma, and Immunology, American College of Allergy, Asthma, and Immunology, and American Academy of Pediatrics all unanimously recommend epinephrine as the only first-line treatment. 1, 2 The FDA-approved labeling for Adrenalin confirms these dosing recommendations and route of administration. 3
What NOT to Do: Common Fatal Pitfalls
Never delay epinephrine administration to give antihistamines, corticosteroids, or bronchodilators first—this practice is directly associated with anaphylaxis fatalities. 1, 2, 6 Antihistamines like diphenhydramine or pheniramine (Avil) are considered solely second-line adjunctive therapy that should never be given before or in place of epinephrine. 1, 2
Never substitute antihistamines for epinephrine. 1, 2 Antihistamines only address non-life-threatening cutaneous symptoms (urticaria, pruritus) and have no effect on airway obstruction or cardiovascular collapse. 1
Do not use subcutaneous epinephrine, as the delayed absorption significantly compromises therapeutic efficacy. 5, 4
Do not inject into the buttocks, deltoid, digits, hands, or feet. 4, 3 The deltoid provides inferior and less consistent absorption compared to the anterolateral thigh. 4
No Absolute Contraindications
There are no absolute contraindications to epinephrine use in anaphylaxis—the benefits always outweigh the risks, even in patients with cardiac disease, advanced age, hypertension, or pregnancy. 1, 2, 4 When treated appropriately with epinephrine, mortality from anaphylaxis is remarkably low at <0.5% per episode. 1
Intravenous Route: Reserved for Refractory Cases Only
Intravenous administration carries significant risks of dilution errors, dosing errors, and serious adverse effects including fatal arrhythmias. 5 This route should be reserved exclusively for severe anaphylaxis unresponsive to intramuscular epinephrine in hospital settings, administered as an infusion at 1-4 mcg/min titrated to a maximum of 10 mcg/min. 4