Overview
Epinephrine is a naturally occurring catecholamine and sympathomimetic agent that acts on both alpha- and beta-adrenergic receptors. It is used in emergency situations such as anaphylaxis, cardiac arrest, and severe asthma exacerbations. It is also used as a vasoconstrictor adjunct to local anesthetics.
Mechanism of Action
Epinephrine stimulates alpha-1, alpha-2, beta-1, and beta-2 adrenergic receptors: Alpha-1: Vasoconstriction → ↑ peripheral vascular resistance and ↑ blood pressure Beta-1: ↑ heart rate, ↑ myocardial contractility, ↑ cardiac output Beta-2: Bronchodilation and inhibition of mediator release from mast cells These combined effects reverse hypotension, bronchospasm, and mucosal edema in anaphylaxis and support circulation in cardiac arrest.
Indications
- Emergency treatment of anaphylaxis (including allergic reactions to foods, drugs, insect stings)
- Cardiac arrest
- Adjunct in local anesthesia to prolong effect and reduce systemic absorption
- Acute treatment of bronchospasm
- Hypotension associated with septic shock (IV infusion in hospital setting)
Dosage
Anaphylaxis (Adults and Children ≥30 kg): 0.3–0.5 mg IM into the anterolateral thigh; may repeat every 5–15 minutes as needed Anaphylaxis (Children 15–30 kg): 0.15 mg IM (auto-injector formulation) Cardiac Arrest (Adults): 1 mg IV/IO every 3–5 minutes Cardiac Arrest (Pediatrics): 0.01 mg/kg IV/IO (0.1 mL/kg of 0.1 mg/mL solution) every 3–5 minutes Adjunct to Local Anesthetics: Concentrations vary (e.g., 1:100,000 or 1:200,000)
Contraindications
- No absolute contraindication in life-threatening anaphylaxis
- Hypersensitivity to epinephrine or any component (rare)
- Caution in patients with severe cardiovascular disease (when not used for emergency indication)
Side Effects
- Tachycardia
- Palpitations
- Hypertension
- Headache
- Anxiety, nervousness
- Tremor
- Injection site reactions
- Arrhythmias (rare but serious)
Interactions
- Beta-blockers: May reduce bronchodilatory effect and cause unopposed alpha stimulation
- MAO inhibitors and tricyclic antidepressants: Potentiate effects
- Halogenated anesthetics: Increased risk of arrhythmias
- Alpha-blockers: May reduce vasoconstrictive effect
Counseling Points
- Life-saving in allergy. Prescription only.