What is the immediate treatment for anaphylaxis?

Immediate Treatment for Anaphylaxis

Administer intramuscular epinephrine immediately into the anterolateral thigh (vastus lateralis) at 0.01 mg/kg (1:1000 concentration), with a maximum single dose of 0.5 mg in adults and 0.3 mg in children—this is the only first-line treatment and must never be delayed. 1, 2

Primary Intervention: Epinephrine Administration

Epinephrine is the cornerstone of anaphylaxis management with no absolute contraindications, regardless of patient age, cardiac disease, or other comorbidities. 1

Dosing and Route

• Intramuscular injection into the vastus lateralis (anterolateral thigh) is the preferred route because it achieves higher peak plasma concentrations more rapidly than subcutaneous or deltoid administration 1
• Adults: 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) 1, 3
• Children: 0.01 mg/kg, maximum 0.3 mg 1
• Autoinjectors deliver fixed doses: 0.3 mg for patients >30 kg and 0.15 mg for children 10-30 kg 1
• Repeat every 5-15 minutes as needed if symptoms persist or progress 1

Critical Timing

Delayed epinephrine administration is directly associated with increased mortality and higher risk of biphasic reactions—do not delay for any reason. 1, 2

Secondary Interventions (After Epinephrine)

Immediate Supportive Measures

• Position patient supine or in Trendelenburg position with legs elevated (unless respiratory distress precludes this) 1, 2
• Establish IV access and administer rapid crystalloid bolus: 500-1000 mL in adults, 10-20 mL/kg in children 1, 2
• Provide supplemental oxygen at 6-8 L/min 1, 2
• Remove or stop the allergen source if ongoing (e.g., stop IV infusion of triggering medication) 1

Adjunctive Medications (Only After Epinephrine)

H1-antihistamines are second-line therapy and should never be administered alone or delay epinephrine: 1

• Diphenhydramine 25-50 mg IV/IM (1-2 mg/kg in children, maximum 50 mg) 1, 2

H2-antihistamines in combination with H1-antihistamines are superior to H1 alone, though evidence for preventing biphasic reactions is lacking: 1, 2

• Ranitidine 50 mg IV over 5 minutes (1 mg/kg in children, diluted in 20 mL) 1, 2

Inhaled beta-2 agonists for persistent bronchospasm after epinephrine: 1, 2

• Albuterol 2.5-5 mg nebulized in 3 mL saline, repeat as needed 1

Refractory Anaphylaxis

For patients not responding to intramuscular epinephrine and IV fluids, consider IV epinephrine infusion (1:10,000 concentration): 1

• IV bolus: 0.05-0.1 mg (50-100 mcg) slowly over several minutes with continuous hemodynamic monitoring 1
• IV infusion: 5-15 mcg/min, titrated to response 1

For patients on beta-blockers with refractory hypotension, administer glucagon: 1

• Adults: 1-5 mg IV over 5 minutes, followed by infusion at 5-15 mcg/min 1
• Children: 20-30 mcg/kg (maximum 1 mg) 1

What NOT to Do

Glucocorticoids have no role in acute anaphylaxis treatment due to slow onset of action (hours) and should never delay or replace epinephrine. 1, 2 Recent evidence shows they do not prevent biphasic reactions and may worsen outcomes when used without adequate epinephrine. 1

Do not use antihistamines or bronchodilators as first-line therapy—they only address specific symptoms and do not prevent progression or mortality. 1, 2

Avoid IV epinephrine outside monitored settings or without proper dilution (use 1:10,000 for IV, never 1:1000). 1, 2

Observation and Disposition

All patients must be observed in a setting capable of managing anaphylaxis until symptoms fully resolve: 1

• Minimum 4-6 hours observation for most patients 1, 2
• Extended observation (6-24 hours) or hospital admission for severe reactions requiring >1 dose of epinephrine, as these patients have 4.8-fold increased risk of biphasic anaphylaxis 1, 2
• Biphasic reactions occur in up to 10% of cases, with mean onset at 11 hours (range up to 72 hours) 1

Discharge Requirements

Every patient discharged after anaphylaxis must receive: 1

• Two epinephrine autoinjectors with proper training on use 1
• Written anaphylaxis emergency action plan 1
• Education on trigger avoidance, recognition of symptoms, and biphasic reactions 1
• Referral to allergist for comprehensive evaluation 1

Common Pitfalls

The most critical error is delaying epinephrine while administering antihistamines or corticosteroids first—this practice significantly increases mortality. 1, 2 Epinephrine is safe even in elderly patients with cardiac disease, whereas delayed treatment is not. 1

Subcutaneous or deltoid injection produces inferior pharmacokinetics compared to intramuscular thigh injection. 1 Always use the vastus lateralis. 1, 2

Premature discharge before symptom resolution or inadequate observation periods miss biphasic reactions. 1 Patients requiring multiple epinephrine doses need extended monitoring. 1, 2