The Pharm So Hard Emergency Medicine & Hospital Pharmacy Podcast

Episode 128. Don't Ask Why Give it in the Thigh!! IM Epinephrine in Anaphylaxis

Jan 28, 2026
They tackle why intramuscular epinephrine in the deltoid often fails and how thigh injections produce much higher plasma levels. They review pharmacokinetic data, absorption physiology, and needle length problems. They debate weight-based versus fixed dosing and argue for larger IM doses in adults to avoid risky IV boluses.
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ANECDOTE

EMS-to-ED Missed Epinephrine Effect

  • Jimmy Pruitt describes an EMS-to-ED handoff where IM epinephrine was given to the left deltoid and the patient didn't improve.
  • He uses this real-world scenario to question whether initial treatment was correct or if escalation was premature.
INSIGHT

Injection Site Determines Epinephrine Exposure

  • Simon and colleagues (2021) found 0.3 mg IM to the deltoid produced plasma Cmax indistinguishable from saline stress levels.
  • IM to the thigh produced roughly tenfold higher Cmax (~12,000 vs ~1,800), showing site drives absorption magnitude.
INSIGHT

Arm IM Is Unpredictable Versus Thigh IM

  • Subcutaneous deltoid injections showed unpredictable absorption and sometimes higher Cmax than deltoid IM, but neither matched thigh IM levels.
  • This underscores how erratic arm dosing can be and why thigh IM is superior.
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