What is the recommended dose and administration of epinephrine (Epi) via intramuscular (IM) injection for anaphylaxis?

Intramuscular Epinephrine for Anaphylaxis

Administer epinephrine 0.3-0.5 mg (adults ≥30 kg) or 0.01 mg/kg up to 0.3 mg (children <30 kg) intramuscularly into the anterolateral thigh immediately upon recognition of anaphylaxis, and repeat every 5-10 minutes as needed. 1, 2

Dosing by Weight

Adults and children ≥30 kg (66 lbs):

• Dose: 0.3-0.5 mg of 1:1000 epinephrine (0.3-0.5 mL) 2
• Autoinjector: 0.3 mg (EpiPen) 3, 4

Children <30 kg (66 lbs):

• Dose: 0.01 mg/kg of 1:1000 epinephrine, maximum 0.3 mg per injection 2
• Autoinjector dosing:
  • 10-25 kg: 0.15 mg (EpiPen Jr) 3
  • ≥25 kg: 0.3 mg (EpiPen) 3

Administration Technique

Site of injection:

• Inject into the anterolateral aspect of the mid-thigh (vastus lateralis muscle) 1, 2
• This is the ONLY recommended site—never inject into the deltoid, subcutaneous tissue, buttocks, digits, hands, or feet 1, 2
• Can be administered through clothing if necessary 4, 2

Why the lateral thigh is critical:

• Intramuscular injection in the vastus lateralis achieves peak plasma concentrations in 8±2 minutes 1, 3
• Subcutaneous injection in the deltoid takes 34±14 minutes to reach peak levels (range: 5-120 minutes), which is dangerously slow 1
• Use a needle at least 1/2 to 5/8 inch long to ensure intramuscular delivery 2

Repeat Dosing

Repeat every 5-10 minutes if:

• Symptoms persist, worsen, or recur 1, 4, 2
• No response to initial dose 1
• Approximately 7-18% of patients require more than one dose 1

Important: If EMS arrival will exceed 5-10 minutes and the patient has not responded to the initial dose, administer a repeat dose 1

Critical Timing Considerations

Epinephrine must be given FIRST—do not delay for antihistamines or corticosteroids:

• Delay in epinephrine administration is associated with anaphylaxis fatalities 3, 4, 5
• Epinephrine is most effective when given immediately after symptom onset 6
• Approximately 500-1000 people die annually in the United States from anaphylaxis 1

Concurrent Management

Immediately after epinephrine administration:

• Activate emergency medical services (call 911) 1, 4
• Position patient supine with legs elevated (unless respiratory distress prevents this) 4
• Monitor clinically for reaction severity and cardiac effects 2

Common Pitfalls to Avoid

Do NOT:

• Use subcutaneous route instead of intramuscular—this delays absorption by 26 minutes 1, 3
• Inject into the deltoid or other sites—only the lateral thigh provides rapid absorption 1
• Administer repeated injections at the same site—this causes vasoconstriction and potential tissue necrosis 2
• Delay epinephrine while giving antihistamines first—this increases mortality 3, 4, 5
• Use ampule/syringe/needle instead of autoinjector in community settings—this causes significant delays and dosing errors 3

Autoinjector dosing challenges:

• Fixed doses (0.15 mg and 0.3 mg) may result in underdosing in adolescents or overdosing in small children 1
• However, slight overdosing is preferable to underdosing during life-threatening anaphylaxis 3
• The 1.5-inch needle on autoinjectors may not reach muscle in obese adolescents 1

No Absolute Contraindications

Epinephrine has NO absolute contraindications for anaphylaxis treatment:

• Use even in patients with cardiac disease, advanced age, or frailty 3
• The risk of death from untreated anaphylaxis far exceeds the risk of epinephrine-related cardiac effects 4
• Serious adverse effects attributed to epinephrine typically follow large intravenous overdoses, not appropriate intramuscular dosing 1

Post-Treatment Requirements

All patients must:

• Be transported to the emergency department via EMS for observation, even if symptoms completely resolve 4
• Receive a prescription for two epinephrine autoinjectors at discharge 4
• Biphasic reactions can occur up to 72 hours later (mean 11 hours) 3