What is the immediate treatment for anaphylaxis?

Immediate Treatment for Anaphylaxis

Intramuscular epinephrine administered immediately into the lateral thigh is the first-line and only life-saving treatment for anaphylaxis—do not delay administration for any reason. 1, 2

Primary Treatment: Epinephrine

Epinephrine must be given first, before any other medication. 1, 2

Administration Details

• Route: Intramuscular injection into the lateral thigh (vastus lateralis)—this is superior to subcutaneous administration due to faster absorption 1, 2
• Dose: 0.01 mg/kg of 1:1000 concentration 1, 2
  • Adults: 0.3-0.5 mg (maximum 0.5 mg per dose) 1, 2, 3
  • Children 10-25 kg: 0.15 mg via autoinjector 1
  • Children/adults ≥25 kg: 0.3 mg via autoinjector 1

Repeat Dosing

• Repeat epinephrine every 5-15 minutes if symptoms persist or recur 1, 2
• If initial dose fails and EMS arrival exceeds 5-10 minutes, a repeat dose should be considered 1
• Multiple doses are frequently required and should not be withheld 2, 4

Critical Pitfall to Avoid

Delayed epinephrine administration is directly associated with fatal outcomes—do not wait to see if symptoms resolve, do not substitute antihistamines or corticosteroids, and do not delay for diagnostic confirmation 1, 2

Immediate Supportive Measures

While administering epinephrine, simultaneously:

• Activate emergency response system (call 911) 1
• Position patient supine with legs elevated (if tolerated and no respiratory distress) 1
• Remove or stop the allergen exposure if identifiable 1

Adjunctive Therapies (Second-Line Only)

These should NEVER be given alone or before epinephrine—they are supplemental treatments only. 1, 2

H1 Antihistamines

• Diphenhydramine 1-2 mg/kg (maximum 50 mg) IV or oral 1, 2
• Oral liquid formulations are absorbed faster than tablets 1
• These have much slower onset than epinephrine and do not prevent progression of anaphylaxis 1, 2

H2 Antihistamines

• Ranitidine 1 mg/kg (12.5-50 mg in children, 50 mg in adults) IV over 5 minutes 1
• Combination of H1 + H2 antihistamines is superior to H1 alone, but both remain second-line to epinephrine 1, 2

Bronchodilators

• Albuterol nebulized (1.5 mL in children, 3 mL in adults) or MDI (4-8 puffs in children, 8 puffs in adults) 1
• Consider for bronchospasm resistant to adequate epinephrine doses 1

Supplemental Oxygen

• Administer to all patients with respiratory symptoms 1

IV Fluid Resuscitation

• Large volume crystalloid infusion for hypotension, orthostasis, or incomplete response to IM epinephrine 1, 4

Management of Refractory Cases

Persistent Hypotension Despite Epinephrine

• Consider IV epinephrine infusion (requires continuous hemodynamic monitoring) 1, 4
• Vasopressor infusion (e.g., dopamine 2-20 mcg/kg/min titrated to maintain systolic BP >90 mmHg) 1, 2

Patients on Beta-Blockers

• Glucagon 1-5 mg IV over 5 minutes (20-30 mcg/kg in children, maximum 1 mg), followed by infusion (5-15 mcg/min) 1, 2
• Beta-blockers can render patients resistant to epinephrine effects 1, 2

Cardiopulmonary Arrest

• High-dose IV epinephrine (1-3 mg of 1:10,000 dilution slowly over 3 minutes, then 3-5 mg, then 4-10 mg/min infusion) 1
• Prolonged resuscitation efforts are encouraged as outcomes are better in anaphylaxis-related arrest 1

Corticosteroids: Limited Role

• Systemic corticosteroids have NO role in acute anaphylaxis management due to slow onset of action (hours) 2
• May be considered for patients with history of idiopathic anaphylaxis, asthma, or severe/prolonged reactions to potentially prevent biphasic reactions 1, 2
• If given: 1-2 mg/kg/day IV divided every 6 hours or prednisone 0.5 mg/kg orally for less critical episodes 1, 2
• Evidence for preventing biphasic reactions is weak and conflicting 1

Observation and Disposition

• All patients must be transported to an emergency department for observation, even if symptoms resolve 1, 5
• Minimum observation period: 4-6 hours for most patients 1, 5
• Prolonged observation or admission warranted for: severe symptoms, multiple epinephrine doses required, history of biphasic reactions, poorly controlled asthma, or delayed initial treatment 1, 5
• Biphasic reactions occur in 1-20% of cases, typically around 8 hours after initial reaction but can occur up to 72 hours later 1

Discharge Requirements

Every patient must leave with:

• Two epinephrine autoinjectors (risk of recurrence or biphasic reaction) 1
• Written anaphylaxis emergency action plan 1
• Referral to allergist for trigger identification and long-term management 1
• Education on autoinjector use and when to administer 1

Key Clinical Pitfalls

• Using subcutaneous instead of intramuscular route—delays absorption and therapeutic effect 2
• Administering IV epinephrine outside monitored settings—only appropriate for cardiac arrest or refractory shock 1, 2, 4
• Relying on antihistamines or corticosteroids as primary treatment—these do not prevent fatal outcomes 1, 2
• Inadequate observation periods—biphasic reactions can be life-threatening 1, 5
• Failing to prescribe autoinjectors at discharge—patients remain at risk for recurrent reactions 1