Is an EpiPen (epinephrine) administered subcutaneously (sub q) or intramuscularly (IM)?

EpiPen Administration: Intramuscular (IM) Injection is Required

EpiPen should be administered intramuscularly (IM) into the anterolateral thigh, not subcutaneously (sub q). This recommendation is based on strong evidence showing significantly faster absorption and higher peak plasma concentrations when epinephrine is delivered intramuscularly 1.

Evidence Supporting Intramuscular Administration

Pharmacokinetic Evidence

• In a prospective, randomized, blinded study of children at risk for anaphylaxis, the time to maximum epinephrine concentration was:

  • 8 ± 2 minutes after IM injection in the vastus lateralis (thigh)
  • 34 ± 14 minutes (range: 5-120 minutes) after subcutaneous injection in the deltoid region 1

• Similar findings were confirmed in a randomized, double-blind, placebo-controlled crossover study in adults 2

Specific Anatomical Location

• The preferred site is the mid-outer thigh (vastus lateralis muscle) 1
• The needle should be long enough (at least 1/2 inch to 5/8 inch) to ensure the injection reaches muscle tissue 3
• The standard EpiPen needle length (1.43 cm or approximately 0.56 inches) is designed specifically for intramuscular delivery 1

Administration Technique

Proper Technique

• Hold the EpiPen firmly against the anterolateral thigh
• Can be administered through clothing if necessary 3
• Hold in place for 3 seconds after triggering 4
• When administering to a child, hold the leg firmly in place to limit movement during injection 3

Body Position Considerations

• Body position (standing, sitting, or supine) does not significantly affect the distance between skin and thigh muscle in adults 5
• For hypotensive patients, a supine position with legs elevated is recommended 4

Dosing Guidelines

Adults and Children ≥30 kg (66 lbs)

• 0.3-0.5 mg (0.3-0.5 mL) of epinephrine 3
• Maximum 0.5 mg per injection 3

Children <30 kg (66 lbs)

• 0.01 mg/kg (0.01 mL/kg) of epinephrine 3
• Maximum 0.3 mg (0.3 mL) per injection 3

Special Considerations

Pediatric Patients

• For children under 15 kg, particularly those under 10 kg, there's a risk that the standard 12.7 mm needle length may reach bone 6
• Approximately 60% of children <10 kg and 19% of those weighing 10-14.9 kg have a skin-to-bone depth less than 12.7 mm 6
• Despite this concern, the benefits of prompt epinephrine administration outweigh the risks in anaphylaxis

Repeat Dosing

• May be repeated every 5-10 minutes as necessary 3
• Do not administer repeated injections at the same site, as vasoconstriction may cause tissue necrosis 3

Common Pitfalls to Avoid

1. Delayed administration: Failure to inject epinephrine promptly contributes to anaphylaxis fatalities 7

2. Subcutaneous injection: This leads to delayed absorption and potentially inadequate response 1

3. Intravenous administration: This route carries risks of dilution errors and dosing errors, with potentially serious adverse effects 1

4. Incorrect site: Injection into the buttocks or deltoid is less effective than thigh injection 1, 2

5. Outdated devices: While not ideal, outdated EpiPens can usually be administered safely if no alternative is available 8

Remember that there are no absolute contraindications to epinephrine administration in anaphylaxis 1, 4. Even in patients with cardiac disease or other conditions where epinephrine might typically be used with caution, the benefits outweigh the risks in true anaphylaxis.