Final answer:
The primary injection site for an auto-injector like an EpiPen® that delivers epinephrine is the lateral portion of the thigh.
Step-by-step explanation:
When using an auto-injector to administer epinephrine, the recommended and primary injection site is the lateral portion of the thigh. This is because the thigh muscle, specifically the vastus lateralis muscle, is large and well-perfused, allowing for rapid absorption of the medication. EpiPens® are commonly prescribed for individuals with severe allergies, and they are designed for ease of use. The device can inject through clothing in emergency situations, which is critical during an anaphylactic reaction when time is of the essence. It is lifesaving to have an epinephrine injector ready, especially for those who are at risk of severe allergic reactions and anaphylaxis. The effects of epinephrine include constricting blood vessels to counteract a drop in blood pressure, relaxing muscles in the lungs to improve breathing, and reducing swelling that could block airways.