Immediate Treatment for Anaphylaxis
Intramuscular epinephrine is the only first-line treatment for anaphylaxis and must be administered immediately—all other interventions are secondary and should never delay epinephrine. 1, 2
Primary Intervention: Epinephrine Administration
Administer epinephrine 0.01 mg/kg intramuscularly (1:1000 concentration) into the vastus lateralis (anterolateral thigh) immediately upon recognition of anaphylaxis. 1, 2
Dosing specifics:
- Adults and children >50 kg: 0.5 mg maximum single dose 1
- Children 25-50 kg: 0.3 mg (or 0.3 mg autoinjector) 1
- Children 10-25 kg: 0.15 mg (or 0.15 mg autoinjector) 1
Repeat epinephrine every 5-15 minutes if symptoms persist or progress—there are no absolute contraindications to epinephrine in anaphylaxis, regardless of age, cardiac disease, or other comorbidities. 1
Critical route consideration:
The intramuscular thigh route achieves higher plasma epinephrine levels more rapidly than subcutaneous or arm injections, making it the preferred route for first-aid treatment. 1, 2 The FDA-approved indication confirms epinephrine is the emergency treatment for Type I allergic reactions including anaphylaxis. 3
Immediate Secondary Actions (After Epinephrine)
Activate emergency medical services immediately—anaphylaxis can be fatal and may require advanced interventions including intubation, vasopressors, or IV epinephrine infusion. 1
Position the patient supine with legs elevated (unless respiratory distress prevents this positioning) to counteract hypotension. 1, 2
Establish IV access and administer rapid crystalloid bolus: 500-1000 mL in adults, 10-20 mL/kg in children. 1, 2 This addresses the profound intravascular volume depletion characteristic of anaphylaxis. 4
Provide supplemental oxygen at 6-8 L/min for patients with respiratory symptoms. 1, 2
Adjunctive Treatments (Never Replace or Delay Epinephrine)
For bronchospasm resistant to epinephrine:
Administer inhaled albuterol (2.5-5 mg nebulized in children, 3 mL in adults) only after epinephrine has been given. 1, 2
Antihistamines (second-line only):
Consider H1 antihistamine (diphenhydramine 1-2 mg/kg, maximum 50 mg IV) plus H2 antihistamine (ranitidine 1 mg/kg or 50 mg IV over 5 minutes)—the combination is superior to H1 alone, but these only address cutaneous manifestations and have no life-saving effects. 1, 2 The evidence supporting antihistamines in anaphylaxis is indirect and limited. 1
Glucocorticoids:
Do NOT routinely administer glucocorticoids—they have no role in acute anaphylaxis treatment due to slow onset of action and do not prevent biphasic reactions. 1, 2 Multiple systematic reviews confirm glucocorticoids lack clear evidence for preventing biphasic anaphylaxis. 1
Refractory Anaphylaxis Management
For patients requiring >1 dose of epinephrine or with persistent hypotension despite IM epinephrine and fluids, consider IV epinephrine infusion (1:10,000 concentration, NOT 1:1000) with continuous hemodynamic monitoring. 1, 2
For patients on beta-blockers with refractory symptoms, administer glucagon 1-5 mg IV over 5 minutes (20-30 mcg/kg in children, maximum 1 mg) followed by infusion at 5-15 mcg/min. 1
Observation and Disposition
Observe all patients for a minimum of 4-6 hours in a monitored setting capable of managing anaphylaxis until symptoms have completely resolved. 1, 2
Extend observation to 6-24 hours for patients with severe anaphylaxis or those requiring >1 dose of epinephrine, as these patients have significantly higher risk of biphasic reactions (odds ratio 4.82). 1, 2 Approximately 7-18% of anaphylaxis patients require a second epinephrine dose, and 10% develop biphasic reactions occurring up to 72 hours later (mean 11 hours). 1
Critical Pitfalls to Avoid
Never delay epinephrine administration—delayed epinephrine is the primary factor associated with anaphylaxis fatalities. 1, 2, 5, 6 Approximately 500-1000 people die annually in the United States from anaphylaxis, with most fatalities resulting from delayed epinephrine and severe cardiorespiratory complications. 1
Never administer antihistamines or glucocorticoids first or alone—these have no life-saving effects and their use instead of epinephrine significantly increases mortality risk. 1, 2, 4
Never use 1:1000 epinephrine concentration for IV administration—only 1:10,000 dilution should be used intravenously to avoid cardiac complications. 1, 2
Never assume resolution after initial improvement—biphasic reactions can occur hours later, requiring continued observation and discharge with epinephrine autoinjectors. 1