What is the dosage of epinephrine (adrenaline) for acute allergic reactions such as anaphylaxis?

Epinephrine Dosing for Anaphylaxis

Administer intramuscular epinephrine at 0.01 mg/kg of 1:1000 concentration (1 mg/mL) into the anterolateral thigh (vastus lateralis), with maximum doses of 0.5 mg in adults and 0.3 mg in children and teenagers, and repeat every 5-15 minutes if symptoms persist. 1

Specific Dosing by Weight

• Adults (≥30 kg or 66 lbs): 0.3-0.5 mg (0.3-0.5 mL) intramuscularly 2
• Children (<30 kg or 66 lbs): 0.01 mg/kg (0.01 mL/kg), up to maximum 0.3 mg 2
• Autoinjector dosing for children:
  • 0.15 mg for children weighing 10-25 kg 3
  • 0.3 mg for children weighing ≥25 kg 3

Route and Site of Administration

The intramuscular route in the lateral thigh is mandatory—not optional—as it achieves peak plasma concentrations in 8±2 minutes versus 34±14 minutes with subcutaneous administration. 3 The anterolateral thigh (vastus lateralis muscle) is the only recommended injection site. 1

• Never inject into buttocks, digits, hands, or feet 2
• Intramuscular administration in the thigh produces significantly higher and more rapid peak plasma epinephrine concentrations compared to subcutaneous or intramuscular injection in the arm 1

Repeat Dosing

Administer additional doses every 5-15 minutes if anaphylaxis signs or symptoms persist. 1 The 5-minute interval can be shortened if clinically appropriate. 1

• Approximately 7-18% of patients require more than one dose of epinephrine 4, 5
• Patients requiring multiple doses have significantly higher risk of biphasic reactions (odds ratio = 4.82) 1

Critical Clinical Considerations

There are no absolute contraindications to epinephrine use in anaphylaxis—even in patients with cardiac disease, advanced age, pregnancy, or other comorbidities. 1, 4 The benefits of prompt administration far outweigh the risks of transient adverse effects. 5

Delayed epinephrine administration is the primary factor associated with anaphylaxis fatalities. 1 Mortality from anaphylaxis is remarkably low at <0.5% per episode when treated appropriately with epinephrine. 4, 5

Adjunctive Therapies (Secondary to Epinephrine)

After epinephrine administration:

• Position: Place patient supine with lower limbs elevated (if cardiovascular symptoms predominate) 1
• Oxygen: Administer to patients with respiratory distress 1
• IV fluids: Give normal saline early with first epinephrine dose for cardiovascular involvement; repeat if severe anaphylaxis with respiratory presentation requires second epinephrine dose 1
• Inhaled beta-2 agonists: For lower respiratory symptoms (wheezing, chest tightness, shortness of breath) after initial epinephrine 1

Antihistamines and glucocorticoids should never be administered before or in place of epinephrine—they are second-line adjunctive therapies only, with no proven role in acute anaphylaxis treatment or prevention of biphasic reactions. 1, 4

Observation and Biphasic Reactions

Observe patients until all signs and symptoms have completely resolved. 1 For severe anaphylaxis or patients requiring >1 dose of epinephrine, extend observation up to 6 hours or longer (including hospital admission) to monitor for biphasic reactions. 1

• Biphasic anaphylaxis occurs in approximately 10.3% of cases, with mean onset at 11 hours (range up to 72 hours) 1
• Risk factors include: severe initial presentation, >1 dose of epinephrine required, wide pulse pressure, unknown trigger 1

Common Pitfalls to Avoid

• Delaying epinephrine while giving antihistamines or corticosteroids first—this increases mortality 4, 6
• Using subcutaneous instead of intramuscular route—this significantly delays absorption and therapeutic effect 3, 4
• Injecting in the arm instead of thigh—this produces inferior pharmacokinetics 1
• Underdosing in adults or overdosing in small children due to fixed-dose autoinjectors 3, 5
• Failing to repeat doses when symptoms persist—approximately 7-18% of patients need multiple doses 4, 5