What is the proper administration and dosage of adrenaline (epinephrine) for treating anaphylaxis?

Adrenaline (Epinephrine) Administration for Anaphylaxis

Inject epinephrine intramuscularly into the mid-outer thigh (vastus lateralis) immediately upon recognizing anaphylaxis—this is the only first-line treatment and delays in administration are associated with increased mortality. 1, 2, 3

Dosing

Adults and Adolescents (≥30 kg)

• 0.3-0.5 mg of 1:1000 concentration (1 mg/mL) intramuscularly 4, 1
• Maximum single dose: 0.5 mg for adults >50 kg 3
• Standard autoinjector delivers 0.3 mg 1

Children (<30 kg)

• 0.01 mg/kg of 1:1000 concentration, up to maximum 0.3 mg 1, 4, 3
• For autoinjectors: 0.15 mg dose for children 10-25 kg (or 7.5-15 kg with newer formulations) 2, 3
• Switch to 0.3 mg autoinjector at approximately 25 kg body weight 2

Repeat Dosing

• Repeat every 5-15 minutes if symptoms persist or recur 1, 4
• Approximately 7-18% of patients require more than one dose 3, 5
• No maximum number of doses—continue until response achieved 1

Administration Technique

Route and Site

• Intramuscular injection into the anterolateral thigh (vastus lateralis muscle) is mandatory 1, 2, 4
• IM thigh injection achieves peak plasma levels at 8±2 minutes versus 34±14 minutes for subcutaneous injection 2
• Never inject into buttocks, digits, hands, or feet 4
• Avoid deltoid (arm) injection—does not achieve adequate plasma levels 1

Autoinjector Use

• Autoinjectors are preferred over ampule/syringe due to faster administration and fewer dosing errors 2
• Inject through clothing if necessary—do not delay 1

Patient Positioning

• Place patient supine (on back) or in position of comfort if respiratory distress present 1
• Elevate lower extremities if tolerated 1
• Never allow patient to stand, walk, or run—sudden position changes can precipitate cardiovascular collapse 1

Intravenous Epinephrine (Severe/Refractory Cases Only)

When to Consider IV Route

• Reserved for patients with cardiovascular collapse unresponsive to IM doses 1
• Requires continuous hemodynamic monitoring 1
• Higher risk of cardiac arrhythmias and adverse effects 1

IV Dosing

• Initial bolus: 0.05-0.1 mg (50-100 mcg) for adults 1
• Infusion: 1-4 mcg/min, titrated up to maximum 10 mcg/min 1, 2
• Prepare by adding 1 mg epinephrine to 250 mL D5W (4 mcg/mL concentration) 1
• Pediatric dosing: 0.01 mg/kg up to 10 mcg/min 1

Critical Clinical Considerations

No Absolute Contraindications

• There are NO absolute contraindications to epinephrine in anaphylaxis 3, 5
• Use even in patients with cardiac disease, advanced age, hypertension, or pregnancy 2, 5
• Benefits far outweigh risks of transient adverse effects 5

Common Pitfalls to Avoid

• Never delay epinephrine to give antihistamines or corticosteroids first—these are only adjunctive therapies 3
• Do not use subcutaneous route—absorption is too slow 2, 6
• Do not underdose due to fear of side effects—prompt administration prevents mortality 1, 2
• Ensure needle length adequate to reach muscle (especially in obese patients) 6

Risk Factors for Fatal Anaphylaxis

• Adolescence 1
• Concomitant asthma (especially poorly controlled) 1
• Delayed epinephrine administration 1, 2, 5
• Failure to carry/use autoinjector 1

Post-Injection Management

Monitoring

• Transport ALL patients to emergency department, preferably by EMS 1
• Monitor for biphasic reactions (occur in up to 20% of cases, mean onset 11 hours, can occur up to 72 hours later) 2
• Patients requiring >1 dose have higher risk of biphasic reactions and hospital admission 2, 5

Adjunctive Therapies (After Epinephrine)

• Supplemental oxygen 1
• IV fluid resuscitation for hypotension 1
• H1-antihistamines for cutaneous symptoms only 3
• Corticosteroids may prevent protracted/biphasic reactions (though not proven) 1
• Bronchodilators for persistent bronchospasm 1

Special Populations

Infants <15 kg

• Current 0.15 mg autoinjector may represent relative overdose for smallest infants 2, 5
• However, benefits still outweigh risks—do not withhold treatment 5
• Newer 0.1 mg formulations becoming available 3

Patients on Beta-Blockers

• May have diminished response to epinephrine 4
• May require higher or more frequent doses 4
• Consider glucagon as adjunct 1

Adverse Effects (Transient and Acceptable)

• Pallor, tremor, anxiety, palpitations, headache, nausea 2, 5
• These effects cannot be separated from therapeutic effects 5
• Serious cardiac events (arrhythmias, myocardial infarction) are rare and risk is far lower than mortality from untreated anaphylaxis 4, 7