epinephrine
Adrenergic agonist (catecholamine)· Brands: Adrenalin, EpiPenIMIVSC
Mechanism of action
Epinephrine is a non-selective adrenergic agonist that acts on alpha and beta receptors. Alpha-1 stimulation causes vasoconstriction, beta-1 stimulation increases heart rate and contractility, and beta-2 stimulation causes bronchodilation and relaxation of uterine smooth muscle. At low doses, beta effects predominate; at higher doses, alpha effects become more pronounced, leading to increased systemic vascular resistance and blood pressure.
Pharmacokinetics
Epinephrine has a rapid onset and short duration of action. After intravenous administration, effects occur within minutes. It is rapidly metabolised by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) in the liver and other tissues. Metabolites are excreted in the urine. It is not effective orally due to extensive first-pass metabolism. Intramuscular and subcutaneous routes provide slower absorption compared with intravenous.
Indications & dosing
Anaphylaxis (Adult)
Use 1:1000 (1 mg/mL) solution. Immediate IM injection into lateral thigh. Repeat every 5-15 min if needed.
- adult · IM: 0.3–0.5 mg single, repeat PRN · Use 1:1000 (1 mg/mL) solution. Immediate IM injection into lateral thigh. Repeat every 5-15 min if needed.
Anaphylaxis (Pediatric)
Max 0.5 mg. Use 1:1000 solution. Repeat every 5-15 min if needed.
- pediatric · IM: 0.01 mg/kg single, repeat PRN · Max 0.5 mg. Use 1:1000 solution. Repeat every 5-15 min if needed.
Cardiac arrest (Adult)
Use 1:10,000 solution. Administer via IV/IO push. Follow with flush.
- adult · IV: 1 mg every 3-5 min · Use 1:10,000 solution. Administer via IV/IO push. Follow with flush.
Cardiac arrest (Pediatric)
Use 1:10,000 solution. Administer via IV/IO push. Follow with flush.
- pediatric · IV: 0.01 mg/kg every 3-5 min · Use 1:10,000 solution. Administer via IV/IO push. Follow with flush.
Croup (Pediatric)off-label
Use 1:1000 solution via nebuliser. Repeat after 20 minutes if needed. Off-label use.
- pediatric · NEB: 0.5–5 mg single, repeat PRN · Use 1:1000 (1 mg/mL) solution via nebuliser, 0.5 mg/kg (max 5 mg), diluted to 2-5 mL as required. Repeat after 20-30 minutes if needed. Off-label use.
Severe asthma (Adult)
For severe exacerbation when inhaled beta-agonists inadequate. May be repeated up to 3 doses.
- adult · SC: 0.3–0.5 mg every 20 min PRN · For severe exacerbation when inhaled beta-agonists inadequate. May be repeated up to 3 doses.
Severe asthma (Pediatric)
Max 0.5 mg. Repeat up to 3 doses.
- pediatric · SC: 0.01 mg/kg every 20 min PRN · Max 0.5 mg. Repeat up to 3 doses.
Contraindications & precautions
- Pheochromocytoma · Catecholamine excess may exacerbate tumour-induced hypertension; use only in life-threatening anaphylaxis.
- Severe coronary artery disease · Risk of myocardial ischaemia; titrate carefully if use unavoidable.
- Narrow-angle glaucoma · May precipitate angle closure; use in anaphylaxis as risks outweigh.
- Hyperthyroidism · Enhanced sensitivity to catecholamines; monitor for arrhythmias.
- Severe hypertension · May cause hypertensive crisis; use with extreme caution if emergency.
- Use with caution in patients with cardiovascular disease (e.g., ischaemic heart disease, arrhythmias), hypertension, hyperthyroidism, or diabetes mellitus.
- Monitor blood pressure and heart rate during therapy when possible.
- Ensure correct dose and route; in anaphylaxis, give IM into the anterolateral thigh, not IV unless under specialised supervision.
- Avoid extravasation; if it occurs, infiltrate with phentolamine to prevent tissue necrosis.
- Use with caution in the elderly and in patients with a history of psychiatric disorders.
Adverse effects
- Tachycardia
- Palpitations
- Tremor
- Anxiety
- Hypertension
- Ventricular arrhythmiasserious
- Myocardial ischaemia or infarctionserious
- Pulmonary oedemaserious
- Cerebral haemorrhageserious
- Injection site necrosisserious
Monitoring, pregnancy & toxicity
- Blood pressure · Continuous during infusion or frequently after bolus
- Heart rate · Continuous during infusion or frequently after bolus
- ECG · Continuous during infusion or as clinically indicated
- Blood glucose · Monitor in prolonged use or in diabetes
- Injection site for extravasation · Assess regularly during infusion
- Pregnancy: Epinephrine is indicated in pregnancy for life-threatening emergencies such as anaphylaxis. It is not contraindicated; the benefits generally outweigh the potential risks. It may cause transient reduction in uterine blood flow but this is acceptable in an emergency.
- Toxicity: Tachycardia and hypertension · Supportive care, monitor vital signs, treat with short-acting antihypertensives if severe
- Toxicity: Cardiac arrhythmias · Manage according to resuscitation protocols; correct hypoxia and electrolyte imbalances
- Toxicity: Myocardial ischaemia and angina · Stop infusion, administer oxygen, consider nitrates if appropriate
- Toxicity: Hyperglycaemia and hypokalaemia · Monitor blood glucose and potassium, correct with insulin or replacement as needed
Clinical notes
Epinephrine is the first-line treatment for anaphylaxis, administered as an intramuscular injection, typically in the anterolateral thigh. Its use is extended to cardiac arrest, severe asthma exacerbations, and croup. In cardiac arrest, it is given intravenously or intraosseously. Continuous ECG and blood pressure monitoring are recommended during intravenous therapy. Caution is required in patients with coronary artery disease, hypertension, or arrhythmias, as epinephrine may precipitate myocardial ischaemia or ventricular arrhythmias. Dosing is weight-based and should follow local protocols.
Log in to read the full epinephrine monograph
A free account unlocks the complete drug reference, the interaction checker, prescription practice and every other learning tool.
BNF; local formulary