Subcutaneous Epinephrine Dosing in Acute Asthma Exacerbations
The recommended dose of subcutaneous epinephrine (1:1000 concentration) for acute asthma exacerbations is 0.01 mg/kg, typically divided into 3 doses of approximately 0.3 mg administered at 20-minute intervals. 1
Dosing Guidelines
Adults and Children ≥30 kg (66 lbs):
- 0.3 to 0.5 mg (0.3 mL to 0.5 mL) of undiluted epinephrine (1:1000) subcutaneously
- Maximum: 0.5 mg (0.5 mL) per injection
- May repeat every 5-20 minutes as necessary based on clinical response 1, 2
Children <30 kg (66 lbs):
- 0.01 mg/kg (0.01 mL/kg) of undiluted epinephrine (1:1000) subcutaneously
- Maximum: 0.3 mg (0.3 mL) per injection
- May repeat every 5-20 minutes as necessary based on clinical response 2
Administration Technique
- Inject into the anterolateral aspect of the thigh
- Do not administer repeated injections at the same site (risk of tissue necrosis)
- Monitor for cardiac effects and severity of asthma symptoms 2
Clinical Context and Considerations
Role in Treatment Algorithm
Epinephrine is not considered first-line therapy for routine asthma exacerbations. The American Heart Association guidelines position subcutaneous epinephrine as an option for patients with acute severe asthma, particularly when:
- Inhaled β2-agonists have failed to provide adequate response
- In catastrophic sudden severe asthma presentations
- When there is concomitant anaphylaxis or angioedema 1, 3
Efficacy and Safety
- Studies show subcutaneous epinephrine (0.3-0.5 mg) produces effective rapid bronchodilation comparable to selective β2-agonists 4, 5
- In patients with severe airway obstruction (PEFR <120 L/min or <25% predicted), parenteral epinephrine may be superior to aerosol delivery 6
- Despite concerns about cardiovascular side effects, studies suggest epinephrine can be safely used in asthmatics of various ages when patients with recent myocardial infarction or angina are excluded 7
Special Situations
For patients with catastrophic sudden severe asthma (brittle asthma) at risk of sudden death, a management plan may include:
- Preloaded syringe with epinephrine (0.5 mg) for subcutaneous injection
- Patient or relative should be trained in administration
- This should be part of a comprehensive management plan agreed upon by patient, general practitioner, and consultant 1
Important Caveats
- Monitor for potential cardiac effects including increased heart rate, myocardial irritability, and increased oxygen demand
- A retrospective investigation indicated a 4% incidence of serious side effects with IV epinephrine; subcutaneous administration has a better safety profile 1
- There is no evidence that subcutaneous epinephrine has advantages over inhaled β2-agonists in routine asthma management 1
- Low-quality evidence suggests epinephrine and selective β2-agonists have similar efficacy in acute asthma 1, 3
Remember that while epinephrine can be effective in acute severe asthma, selective inhaled β2-agonists remain the first-line bronchodilator therapy for most asthma exacerbations due to their more favorable side effect profile.