What are the guidelines for prescribing EpiPen (epinephrine) doses to adults and children of varying weights?

EpiPen Dosing and Prescribing Guidelines

For children weighing ≥25 kg and adults, prescribe the 0.3 mg EpiPen; for children weighing 10-25 kg, prescribe the 0.15 mg EpiPen Jr. 1

Weight-Based Dosing Algorithm

Children Under 10 kg

• Prescribe the 0.15 mg EpiPen Jr despite exceeding the ideal 0.01 mg/kg dose 2
• The Canadian Society of Allergy and Immunology recommends this approach given the lack of suitable alternatives, as adverse effects (pallor, tremor, anxiety) are expected to be mild and transient compared to the fatal consequences of not receiving epinephrine 2
• Critical caveat: Up to 60% of children <10 kg may have the 12.7 mm needle penetrate bone rather than muscle, though this remains preferable to no treatment 3

Children 10-25 kg

• Prescribe the 0.15 mg EpiPen Jr 1, 4
• This provides approximately 0.01 mg/kg for a 15 kg child, which is the recommended dose 5
• Approximately 19% of children weighing 10-14.9 kg remain at risk of bone penetration with the 12.7 mm needle 3

Children ≥25 kg and Adults <45 kg

• Prescribe the 0.3 mg EpiPen 1, 4
• At 25 kg, the 0.3 mg dose provides 0.012 mg/kg, which is a slight overdose but preferable to underdosing during life-threatening anaphylaxis 1
• The FDA label specifies 0.3 mg for children ≥30 kg (66 lbs), but the American Academy of Pediatrics recommends the lower 25 kg threshold to prevent underdosing 4, 1

Adults ≥45 kg

• Consider prescribing the 0.5 mg EpiPen based on shared decision-making 6
• As weight increases above 30 kg, the 0.3 mg dose increasingly underdoses patients (providing <0.01 mg/kg) 6
• The Canadian Society of Allergy and Immunology recommends the 0.5 mg dose for patients ≥45 kg, though this requires individualized discussion about availability and patient preference 6

Administration Instructions

Route and Site

• Inject intramuscularly into the anterolateral thigh (vastus lateralis muscle) at a 90-degree angle 1, 4
• This route achieves peak plasma concentration at 8±2 minutes versus 34±14 minutes for subcutaneous injection 1
• Never inject into buttocks, digits, hands, or feet 4
• The injection can be administered through clothing if necessary during emergencies 1

Repeat Dosing

• Repeat every 5-10 minutes as necessary if symptoms persist or recur 4, 1
• Patients requiring more than one dose have higher risk of biphasic reactions 1
• Delayed epinephrine administration has been associated with anaphylaxis fatalities 1

Critical Prescribing Considerations

No Absolute Contraindications

• Prescribe epinephrine even in patients with cardiac disease, advanced age, or frailty 1
• The risk of death from untreated anaphylaxis far exceeds the risk of epinephrine adverse effects 1

Expected Adverse Effects

• Common effects include pallor, tremor, anxiety, palpitations, headache, and nausea 5, 7
• These effects cannot be dissociated from therapeutic benefits and are transient 5, 7
• In a prospective study, children receiving 0.3 mg experienced more adverse effects (palpitations, headache, nausea) than those receiving 0.15 mg, but all effects were transient 5, 7

Avoid Ampule/Syringe/Needle Approach

• Do not prescribe epinephrine ampules with syringes for home use 5
• Parents took 142±13 seconds to draw up doses (versus 29 seconds for emergency nurses) and demonstrated nearly 40-fold variation in dose accuracy (0.004 to 0.151 mL when attempting 0.09 mL) 5

Special Populations

Obese Patients

• Limited data suggest 0.3 mg EAI needles may be too short for obese patients >30 kg, potentially resulting in subcutaneous rather than intramuscular delivery 8
• Consider the 0.5 mg formulation which may have a longer needle, though specific needle length data should be verified 6

Patients with Asthma or High-Risk Features

• Consider switching to the higher dose at a lower weight threshold for children with asthma or other risk factors for fatal anaphylaxis 1

Common Pitfalls to Avoid

• Delaying epinephrine while administering antihistamines or corticosteroids first - epinephrine is the only first-line treatment that reverses anaphylaxis 1, 2
• Using subcutaneous instead of intramuscular route - this delays absorption by approximately 26 minutes 1
• Prescribing based on FDA label alone (30 kg threshold) rather than optimal dosing (25 kg threshold) - this results in underdosing many children 1, 4
• Failing to prescribe two autoinjectors - approximately 20-30% of anaphylaxis episodes require a second dose 1