Why do you inject epinephrine into the thigh instead of the arm?

Answer 1

The reason why we now inject epinephrine into the thigh rather than the arm is because injection into the muscle tissue (IM) results in smoother and more reliable drug absorption, with higher peak therapeutic levels of the drug achieved sooner than with subcutaneous injection.

The lateral thigh is often used for the IM injection; the outer upper arm is most commonly used for the subcutaneous(SC) injection. In an "auto-injector pen" used to administer epinephrine (often referred to by the brand name "EpiPen"), the needle may not be long enough to reach the muscle tissue of a large and/or obese person.

However, if the epinephrine is injected into the subcutaneous tissue, it will in all likelihood still be effective, albeit not as quickly as via IM injection.

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