Generic Name

EpiPen

Brand Names

for autoinjectors containing *epinephrine*, a potent adrenergic agonist used for the rapid relief of anaphylaxis and severe allergic reactions. This drug card summarizes its pharmacology, clinical use, and practical considerations for healthcare professionals and medical students.

Mechanism

The key therapeutic actions of epinephrine come from its non‑selective stimulation of α‑1, β‑1, and β‑2 adrenergic receptors:
• α‑1 agonism → vasoconstriction of systemic vasculature → increased intravascular volume and blood pressure; reduced mucosal edema.
• β‑1 agonism → improved myocardial contractility and heart rate → augmented cardiac output.
• β‑2 agonism → bronchodilation and decreased bronchial secretions → alleviation of bronchospasm.

These combined effects quickly reverse the hypotension, bronchoconstriction, and urticaria that characterize anaphylaxis.

Pharmacokinetics

The ultra‑short half‑life underlines the need for the immediate administration of a second dose if clinical improvement is not observed.

Indications

• Anaphylaxis (immediate life‑threatening allergic reaction)
• *Adult*: 0.3 mg IM (EpiPen® 0.3 mg)
• *Child*: 0.15 mg IM (EpiPen® 0.15 mg) for mild–moderate; 0.3 mg for severe cases
• Severe acute bronchospasm or asthma exacerbation when systemic epinephrine is indicated
• Critical hypotension in the setting of anaphylaxis or other severe allergic reactions

EpiPen is the first‑line pharmacologic intervention in all emergency anaphylaxis protocols.

Contraindications

• Absolute contraindications: None (epinephrine is the only lifesaving medication for anaphylaxis).
• Relative contraindications / cautions
• Uncontrolled hypertension, angina, recent myocardial infarction, or significant atherosclerotic disease
• Isolated severe tachyarrhythmias or known cardiac conduction abnormalities
• Use with monoamine oxidase inhibitors (MAOIs) may provoke severe hypertensive crisis
• Warnings
• Not to be used for mild allergic reactions without systemic symptoms
• Not to be self‑administered by untrained individuals for non‑anaphylactic indications
• Requires prompt evaluation in a medical facility after use

Dosing

• Auto‑injector orientation: Hold the device vertically; remove the protective cap; bend the needle slightly (3 cm) to reduce accidental skin injuries.
• Site of injection: Anterior thigh (hamstring) or gluteal muscle in the absence of contraindications.
• Procedure

1. Remove cap and hold epinephrine tuber; inject for at least 10 seconds.

2. Remove the needle with a protective tip; massage the injection site for 30 seconds.

3. Second dose: If symptoms persist or recur after 5–15 minutes, administer a second dose.
• Special populations
• *Infants & children under 15 kg*: EpiPen® 0.15 mg; if size‑appropriate, use 0.3 mg.
• *Pregnancy*: No direct contraindication; benefits outweigh risks in anaphylaxis.

Adverse Effects

• Common
• Palpitations, tachycardia, hypertension
• Anxiety, jitteriness, tremor
• Headache, light‑headedness
• Serious / Rare
• Supraventricular or ventricular arrhythmias
• Myocardial ischemia or infarction (especially in patients with coronary artery disease)
• Angina or chest pain
• Hypersensitivity reactions to the device components (very rare)

Monitoring

Patients should be observed in an emergency setting until symptoms resolve to a stable baseline.

Clinical Pearls

• Never break or modify the dose—auto‑injectors provide the exact therapeutic amount; dilution leads to under‑dosing.
• Teach proper use before discharge—provide a written or visual guide; emphasize expiring dates and correct hand‑hold technique.
• Second dose timing is critical—waiting beyond 15 minutes may delay needed therapy.
• Avoid concurrent MAOI use—if a patient is on MAOIs, a higher risk of hypertensive crisis exists; consider alternative therapy and proceed with caution.
• Use the higher‐dose auto‑injector for patients >30 kg—the 0.3 mg formulation is recommended for adults and heavier children; the 0.15 mg is labeled for light–moderate reactions but can be used in severe reactions under guidance.
• Store at room temperature—do not refrigerate; keep out of direct sunlight or high humidity, as the device’s integrity could be compromised.
• Regulatory updates: In 2024, FDA approved an updated EpiPen Junior® (0.15 mg), specifically designed for children 4–17 kg. Always verify the dosing device matches the patient’s weight.
• Do not use a single-dose syringe for patients with delayed or biphasic anaphylaxis—maintain readiness for repeated dosing.
• Place a vial of 0.5 mg epinephrine on standby for emergency airway compromise where higher dosing may be required; this is an adjunct, not a replacement for the auto‑injector.

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• *This card is intended for educational purposes and should not replace clinical guidelines or individual patient assessment.*