What is the proper prescription sig (directions) for an epinephrine auto‑injector (EpiPen) for adults and children based on weight?

EpiPen Prescription Sig (Directions)

For patients ≥30 kg (66 lbs): Prescribe EpiPen 0.3 mg; inject intramuscularly into outer thigh at first sign of anaphylaxis, may repeat once after 5-15 minutes if symptoms persist or recur, then call 911 immediately. 1

For patients 15-30 kg (33-66 lbs): Prescribe EpiPen Jr 0.15 mg; inject intramuscularly into outer thigh at first sign of anaphylaxis, may repeat once after 5-15 minutes if symptoms persist or recur, then call 911 immediately. 2, 1

Weight-Based Dosing Algorithm

Adults and Children ≥30 kg

• Device: EpiPen 0.3 mg 1
• Route: Intramuscular into anterolateral thigh (outer mid-thigh) 3, 2
• Timing: Immediately at first sign of anaphylaxis (respiratory distress, hypotension, airway swelling, difficulty breathing, or multi-system symptoms) 3
• Repeat dosing: May repeat every 5-15 minutes as needed 3, 2, 1
• Maximum home doses: Two doses maximum before requiring direct medical supervision 1

Children 15-30 kg

• Device: EpiPen Jr 0.15 mg 2, 1
• Route: Intramuscular into anterolateral thigh 2, 1
• Timing: Immediately at first sign of anaphylaxis 2
• Repeat dosing: May repeat every 5-15 minutes as needed 2
• Maximum home doses: Two doses maximum before requiring direct medical supervision 1

Infants and Small Children <15 kg

• Device: EpiPen Jr 0.15 mg (despite exceeding 0.01 mg/kg dosing for smaller infants) 4
• This represents a higher dose per kilogram for infants weighing <15 kg, but the 0.15 mg dose is recommended given lack of suitable alternatives and the fact that adverse effects are expected to be mild and transient compared to the risk of untreated anaphylaxis 4
• A 0.1 mg autoinjector formulation exists but may not be widely available 5, 6

Prescription Sig Examples

For adults/children ≥30 kg: "Inject 0.3 mg intramuscularly into outer thigh at first sign of severe allergic reaction (difficulty breathing, throat tightness, severe hives, dizziness, or low blood pressure). May repeat once after 5-15 minutes if symptoms persist or worsen. Call 911 immediately after first dose. Prescribe 2 auto-injectors."

For children 15-30 kg: "Inject 0.15 mg intramuscularly into outer thigh at first sign of severe allergic reaction (difficulty breathing, throat tightness, severe hives, dizziness, or low blood pressure). May repeat once after 5-15 minutes if symptoms persist or worsen. Call 911 immediately after first dose. Prescribe 2 auto-injectors."

Critical Prescribing Points

Always Prescribe Two Doses

• All patients should receive a prescription for two epinephrine auto-injectors 2
• 6-19% of pediatric patients require a second dose 7
• 17% of emergency department patients with anaphylaxis require additional doses 7

Administration Technique

• Inject through clothing if necessary 1
• Never inject intravenously, into buttocks, digits, hands, or feet 1
• For young children who may be uncooperative: caregivers must firmly hold the leg in place to prevent movement during injection 1
• Intramuscular injection into the anterolateral thigh produces the most rapid peak plasma epinephrine concentrations 3

Emergency Medical Services Activation

• Call 911 immediately after epinephrine administration 2
• All patients who receive epinephrine should proceed to an emergency facility for observation 2
• Recommended observation period: 4-6 hours minimum; longer for severe or refractory symptoms 2

Common Pitfalls to Avoid

Delayed administration: This is the most critical error—delayed epinephrine has been implicated in anaphylaxis fatalities 2. Epinephrine is most effective when given immediately at symptom onset 3.

Relying on antihistamines or bronchodilators alone: These are adjunctive therapies only and should never replace epinephrine as first-line treatment 2, 8.

Incorrect injection site: Subcutaneous injection has delayed onset compared to intramuscular 3. The thigh is superior to other sites 3, 5.

Failing to prescribe two devices: Patients need backup dosing capability since repeat doses are frequently required 2, 7.

Not counseling on when to use: Patients must understand to inject at the first sign of anaphylaxis symptoms involving respiratory distress, cardiovascular symptoms (hypotension, dizziness), or multi-system involvement 3, 2.

No Absolute Contraindications

There are no absolute contraindications to epinephrine in anaphylaxis 8, 7, 5. The benefits vastly outweigh risks even in patients with cardiovascular disease, though providers should counsel appropriately for high-risk patients 5.

Dosing Nuances

The FDA-approved dosing is weight-based using fixed-dose autoinjectors 1. While the theoretical optimal dose is 0.01 mg/kg (maximum 0.3-0.5 mg) 2, 5, the available autoinjector formulations provide 0.15 mg or 0.3 mg fixed doses, which are appropriate for their respective weight ranges despite not being perfectly weight-proportional for all patients 9, 4.

For infants <15 kg, the 0.15 mg dose exceeds the 0.01 mg/kg recommendation but is still recommended as the safest available option, with expected mild transient adverse effects (pallor, tremor, anxiety) that are far preferable to untreated anaphylaxis 4.