Epinephrine (EpiPen) Weight-Based Dosing for Anaphylaxis
For anaphylaxis treatment, epinephrine should be dosed at 0.01 mg/kg (maximum 0.3 mg in prepubertal children and up to 0.5 mg in teenagers), with patients weighing 7.5-25 kg receiving the 0.15 mg auto-injector and those weighing 25 kg or more receiving the 0.3 mg auto-injector. 1, 2
Standard Dosing Guidelines
Intramuscular Injection Dosing
- Adults and children ≥30 kg (66 lbs): 0.3-0.5 mg (0.3-0.5 mL) of 1:1000 concentration
- Children <30 kg (66 lbs): 0.01 mg/kg (maximum 0.3 mg) of 1:1000 concentration 2, 3
Auto-Injector Dosing
- Patients 7.5-25 kg (16.5-55 lbs): 0.15 mg auto-injector
- Patients ≥25 kg (55 lbs): 0.3 mg auto-injector 1
Administration Technique
The preferred route of administration is intramuscular injection into the anterolateral thigh (vastus lateralis muscle), which achieves peak plasma concentrations in approximately 8 ± 2 minutes. This is significantly faster than subcutaneous administration, which can take 34 ± 14 minutes to reach maximum concentration. 1, 2
Key technique points:
- Hold the auto-injector in place for 3 seconds after triggering
- Hold the leg firmly for young children to prevent injection-related injury
- Avoid injection into buttocks, digits, hands, or feet 2, 3
Special Considerations
Pediatric Patients
- For infants and very small children (<15 kg), there is concern that the 12.7 mm needle length of standard auto-injectors may be too long, potentially resulting in intraosseous injection 4
- Approximately 60% of children weighing <10 kg and 19% of those weighing 10-14.9 kg may be at risk of having the auto-injector administered into bone 4
- Despite this concern, the benefit of prompt epinephrine administration outweighs the risk of delayed treatment 1, 2
Obese Patients
- In obese adolescents, especially females, the standard needle length may not reach the muscle, potentially resulting in subcutaneous rather than intramuscular administration 1
- For these patients, healthcare providers should consider this limitation when prescribing auto-injectors 5
Common Pitfalls and Caveats
Delayed administration: Prompt injection of epinephrine is critical; delayed injection is associated with poor outcomes including fatality 1
Inappropriate substitution: H1-antihistamines and bronchodilators are adjunctive treatments and should never replace epinephrine as the initial treatment for anaphylaxis 1, 2
Underdosing in heavy adults: The standard 0.3 mg auto-injector dose may be insufficient for heavy adults based on the 0.01 mg/kg recommendation 6
Repeat dosing: 6-19% of pediatric patients may require a second dose of epinephrine, which should be administered 5-15 minutes after the first if needed 2
Side effects: Common transient side effects include pallor, tremor, anxiety, palpitations, headache, and nausea. More significant side effects are more common with the 0.3 mg dose 2, 7
All patients who receive epinephrine for anaphylaxis should be transported to an emergency department for observation (typically 4-6 hours) with monitoring of vital signs and potential cardiac monitoring, particularly for high-risk patients 2.