Anaphylaxis Treatment Guidelines

Introduction to Anaphylaxis Management

The American Academy of Allergy, Asthma, and Immunology recommends that epinephrine is the only first-line treatment for anaphylaxis, and antihistamines like Avil (pheniramine) are considered solely second-line adjunctive therapy that should never be given before or in place of epinephrine 1, 2

The American College of Allergy, Asthma, and Immunology recommends intramuscular epinephrine should be administered immediately at 0.01 mg/kg of 1:1000 concentration (1 mg/mL), with maximum doses of 0.5 mg in adults and 0.3 mg in children, injected into the anterolateral thigh (vastus lateralis) 1, 2, 3, 4
Adults (>50 kg) should receive a maximum dose of 0.5 mg 3
Children and teenagers should receive a maximum dose of 0.3 mg 4
Infants 7.5-15 kg should receive 0.15 mg (or 0.1 mg with newer formulations) 1, 2
Repeat doses should be administered every 5-15 minutes if symptoms persist 4

Antihistamines may be used as adjunctive therapy only after epinephrine has been administered and the patient is stabilized, and only for addressing cutaneous symptoms 3, 4
H1 antihistamines may help with urticaria, angioedema, and pruritus 3
These medications address only non-life-threatening symptoms 3

Never delay epinephrine while administering antihistamines first, as this is associated with increased mortality 3, 5, 6
Never substitute antihistamines for epinephrine, as there are no absolute contraindications to epinephrine use in anaphylaxis 3, 4, 5
Do not use subcutaneous epinephrine, as intramuscular administration in the lateral thigh provides faster absorption 6

The mortality from anaphylaxis is remarkably low at <0.5% per episode when treated appropriately with epinephrine 5
Approximately 7-18% of patients require more than one dose of epinephrine, and these patients are at higher risk for hospital admission and biphasic reactions 5, 6

The intramuscular route in the lateral thigh achieves peak plasma concentrations in 8±2 minutes, which is critical for reversing life-threatening hypotension and airway obstruction, as recommended by the American Academy of Pediatrics 7
The intramuscular route is vastly superior to subcutaneous injection, with the latter achieving peak plasma concentrations in 34±14 minutes, according to the American Academy of Pediatrics 7

Do not use subcutaneous epinephrine, as the delayed absorption significantly compromises therapeutic efficacy, as stated by the American Academy of Pediatrics 7

Intravenous administration of epinephrine 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, with significant risks of dilution errors, dosing errors, and serious adverse effects including fatal arrhythmias, as noted by the American Academy of Pediatrics 7