How is an EpiPen (epinephrine) used in a healthy adult?

From the Guidelines

An EpiPen should be used immediately when a healthy adult experiences a severe allergic reaction (anaphylaxis), with a dose of 0.01 mg/kg of 1 mg/mL (1:1000), up to 0.5 mg in adults, administered intramuscularly into the vastus lateralis (antero-lateral thigh) 1. To use an EpiPen, first remove the blue safety cap, then firmly press the orange tip against the outer thigh and hold for 3 seconds until you hear a click. The injection can be given through clothing if necessary. After administration, call emergency services immediately and seek medical attention, as the effects of epinephrine are temporary (typically 10-20 minutes). A second dose may be needed if symptoms persist or return before help arrives. Epinephrine works by constricting blood vessels to increase blood pressure, relaxing airway muscles to improve breathing, and reducing hives and swelling. Side effects may include increased heart rate, anxiety, dizziness, and headache, but these are generally outweighed by the life-saving benefits during anaphylaxis. It is essential to note that there are no absolute contraindications to the use of epinephrine for anaphylaxis 1. Additional emergency management includes placing the patient in a supine position if their presentation is mainly cardiovascular, monitoring vital signs, and administration of oxygen to patients with respiratory distress and those receiving further doses of epinephrine 1. Intravenous fluids are to be administered early with the first epinephrine dose to patients with cardiovascular involvement and should be repeated if lack of response 1. Patients with lower respiratory symptoms should receive inhaled beta-2 agonists following initial treatment with epinephrine 1. Clinicians should educate patients and their caregivers about the signs and symptoms of anaphylaxis and provide an emergency action plan that includes instructions for using epinephrine 1. This discussion should be part of the informed consent surrounding allergy treatment and documented in the patient’s medical record. The most recent and highest quality study, published in 2024, provides strong evidence for the use of epinephrine as the first-line treatment for anaphylaxis 1. In contrast, older studies, such as those published in 2007 1 and 2005 1, provide less relevant information due to updates in clinical practice guidelines. Therefore, the recommendation to use an EpiPen in a healthy adult experiencing anaphylaxis is based on the most recent and highest quality evidence available 1.

From the FDA Drug Label

5 WARNINGS AND PRECAUTIONS

5.1 Incorrect Locations of Injection Injection into the anterolateral aspect of the thigh (vastus lateralis muscle) is the most appropriate location for administration because of its location, size, and available blood flow.

The EpiPen (epinephrine) should be used in a healthy adult by injecting into the anterolateral aspect of the thigh (vastus lateralis muscle).

• Do not administer repeated injections of epinephrine at the same site.
• Do not inject into the buttock, as it may not provide effective treatment of anaphylaxis and has been associated with the development of Clostridial infections.
• Do not inject into digits, hands, or feet, as epinephrine is a strong vasoconstrictor and may result in loss of blood flow to the affected area and tissue necrosis 2.

From the Research

EpiPen Use in Healthy Adults

• An EpiPen is a prefilled epinephrine auto-injector used to treat anaphylaxis, a severe and potentially life-threatening allergic reaction 3.
• In healthy adults, an EpiPen is administered via intramuscular injection into the thigh, with a maximal pharmacodynamic effect within 10 minutes 3.
• The dosage of epinephrine in an EpiPen varies, with available doses of 0.15,0.30, and 0.50 mg, and different needle lengths to ensure intramuscular delivery in adults, including obese patients 3.

Administration and Education

• Prompt administration of epinephrine is critical in treating anaphylaxis, and failure to do so can result in fatalities 3, 4, 5.
• Education about anaphylaxis and prompt treatment with epinephrine is essential for patients and their caregivers 3.
• Studies have shown that epinephrine is often underused in treating anaphylaxis, and antihistamines are more commonly used, despite epinephrine being the recommended first-line therapy 4.

Treatment Guidelines

• Current guidelines recommend intramuscular epinephrine as the immediate treatment for anaphylaxis, with intravenous epinephrine used in patients in shock 6.
• The use of corticosteroids in anaphylaxis treatment is still debated, with some studies suggesting a beneficial effect, while others find no compelling evidence to support their use 7, 5.
• Antihistamines may have a beneficial effect in anaphylaxis treatment, but their use should not replace epinephrine as the first-line therapy 4, 5.