Is 1mg of epinephrine (adrenaline) intramuscularly a standard initial dose?

Epinephrine Dosing for Anaphylaxis

1mg of epinephrine intramuscularly is not the standard initial dose for anaphylaxis and exceeds recommended guidelines, potentially causing dangerous cardiovascular side effects.

Correct Epinephrine Dosing for Anaphylaxis

According to the 2020 American Heart Association (AHA) guidelines, the recommended dose of epinephrine for anaphylaxis is:

• Adults and children ≥30 kg: 0.2 to 0.5 mg (1:1000 solution) intramuscularly 1
• Children <30 kg: 0.01 mg/kg intramuscularly 1

The FDA-approved dosing for Adrenalin® (epinephrine) confirms these recommendations:

• Adults and Children ≥30 kg: 0.3 to 0.5 mg intramuscularly 2
• Children <30 kg: 0.01 mg/kg, up to 0.3 mg, intramuscularly 2

Administration Technique

• Inject into the anterolateral aspect of the thigh (vastus lateralis muscle) 1, 2
• Repeat doses every 5-15 minutes as necessary if symptoms persist 1
• Approximately 10-20% of patients may require more than one dose 1

Why 1mg Is Excessive

1mg of epinephrine intramuscularly is twice the maximum recommended dose for adults with anaphylaxis. This excessive dose increases the risk of:

• Anxiety, restlessness, tremor
• Palpitations and tachycardia
• Ventricular arrhythmias
• Hypertension potentially leading to cerebral hemorrhage
• Myocardial ischemia, especially in patients with underlying heart disease 2, 3

Common Pitfalls in Epinephrine Administration

1. Dose confusion: Mixing up cardiac arrest dosing (higher, intravenous) with anaphylaxis dosing (lower, intramuscular) 4

2. Route confusion: Using intravenous administration when intramuscular is indicated for initial treatment 4

3. Delayed administration: Hesitating to give epinephrine is associated with poorer outcomes 5, 6

4. Inadequate monitoring: Patients should be monitored closely after epinephrine administration for both recurrence of anaphylaxis and potential cardiovascular side effects 3

Special Considerations

• For patients not responding to initial IM doses and fluid resuscitation, IV epinephrine may be considered at a much lower dose (0.05 to 0.1 mg) 1

• IV infusion may be reasonable for treatment of anaphylactic shock (5-15 μg/min) when shock persists 1

• H1 antihistamines (diphenhydramine 1-2 mg/kg or 25-50 mg) and H2 blockers are adjunctive treatments only and should never replace epinephrine 1, 7

Algorithm for Anaphylaxis Management

1. Recognize anaphylaxis: Hypotension, airway swelling, difficulty breathing, or multisystem involvement

2. Administer correct epinephrine dose immediately:

   • Adults: 0.3-0.5 mg IM (not 1mg)
   • Children: 0.01 mg/kg IM (max 0.3 mg)

3. Position patient: Recumbent with lower extremities elevated if hypotensive

4. Establish airway and give oxygen if needed

5. Start IV fluids for hypotension (normal saline)

6. Reassess in 5-15 minutes:

   • If symptoms persist → repeat epinephrine dose
   • If no improvement after multiple IM doses → consider IV epinephrine (0.05-0.1 mg)

7. Add adjunctive therapies:

   • H1 antihistamines (diphenhydramine)
   • H2 blockers (ranitidine)
   • Corticosteroids
   • Bronchodilators for bronchospasm

Remember that epinephrine is the cornerstone of anaphylaxis treatment, but the correct dose is critical for safety and efficacy.