What is the first-line treatment for an adult or pediatric patient experiencing anaphylaxis, including the recommended dose and administration route of epinephrine (adrenaline)?

Epinephrine Treatment Guide for Anaphylaxis

Epinephrine is the only first-line treatment for anaphylaxis and must be administered immediately—intramuscularly into the anterolateral thigh at 0.01 mg/kg (maximum 0.5 mg in adults, 0.3 mg in children) using 1:1000 concentration—with no acceptable substitutes or delays for antihistamines or other medications. 1, 2, 3

Immediate Administration Protocol

Dosing by Weight

• Adults and patients >50 kg: 0.5 mg (0.5 mL of 1:1000 solution) intramuscularly 1, 2, 3
• Children and teenagers (25-50 kg): 0.3 mg (0.3 mL of 1:1000 solution) intramuscularly 1, 2
• Infants and children (7.5-25 kg): 0.15 mg via autoinjector, or calculate 0.01 mg/kg of 1:1000 solution 1, 2, 4
• All patients: Use 1:1000 concentration (1 mg/mL) for intramuscular injection 1, 3

Injection Site and Technique

• Inject into the vastus lateralis muscle (anterolateral aspect of mid-thigh) at a 90-degree angle to ensure intramuscular delivery, which achieves peak plasma concentrations in 8±2 minutes compared to 34±14 minutes with subcutaneous injection 1, 2, 5
• Never use the subcutaneous route, deltoid muscle, buttocks, digits, hands, or feet 2, 5, 3
• The intramuscular thigh route is vastly superior and provides more rapid, higher peak plasma levels than any alternative site 2, 5

Repeat Dosing

• Administer additional doses every 5-15 minutes if anaphylaxis signs or symptoms persist 1, 3, 6
• Approximately 7-18% of patients require more than one dose and are at higher risk for hospital admission and biphasic reactions 2

Supportive Care Measures

Patient Positioning

• Place the patient supine with legs elevated if cardiovascular symptoms predominate (hypotension, dizziness) 1, 4
• Allow the patient to sit upright if respiratory distress is the primary presentation 1

Monitoring and Additional Interventions

• Establish intravenous access and administer normal saline boluses early with the first epinephrine dose in patients with cardiovascular involvement 1
• Provide supplemental oxygen to patients with respiratory distress and those requiring additional epinephrine doses 1
• Monitor vital signs continuously 1, 4
• Administer inhaled beta-2 agonists (albuterol) for lower respiratory symptoms (wheezing, chest tightness) only after initial epinephrine treatment 1, 4

Adjunctive Medications (Never First-Line)

Antihistamines

• H1-antihistamines may be used only after epinephrine administration for cutaneous symptoms like urticaria, angioedema, and pruritus 1, 2, 4
• Antihistamines should never be administered before or in place of epinephrine, as they address only non-life-threatening symptoms and do not prevent mortality 1, 2, 4

Corticosteroids

• Glucocorticoids have no proven role in treating acute anaphylaxis due to slow onset of action and should never be given before or instead of epinephrine 1
• Neither antihistamines nor glucocorticoids reliably prevent biphasic anaphylaxis 1

Critical Pitfalls to Avoid

Timing and Medication Errors

• Delayed epinephrine administration is directly associated with anaphylaxis fatalities—the mortality rate is <0.5% when treated appropriately with prompt epinephrine 2, 5, 7
• Never substitute antihistamines, corticosteroids, or bronchodilators as first-line treatment 2, 4, 8
• Do not delay epinephrine while waiting to confirm the diagnosis—administer as soon as anaphylaxis is suspected 2, 5, 7

Route and Concentration Errors

• Verify the correct concentration before administration: 1:1000 (1 mg/mL) for intramuscular use and 1:10,000 (0.1 mg/mL) for IV use to avoid potentially fatal overdose 5, 3
• Intravenous epinephrine should be reserved exclusively for severe anaphylaxis unresponsive to intramuscular epinephrine in hospital settings, as it carries significant risks of dilution errors, dosing errors, and fatal arrhythmias 2, 5

Contraindications

• There are no absolute contraindications to epinephrine use in anaphylaxis—the benefits always outweigh the risks, even in patients with cardiovascular disease, hypertension, or those on beta-blockers 1, 4, 5, 3

Post-Anaphylaxis Management

Observation Period

• Observe patients for 4-6 hours minimum in a setting capable of managing anaphylaxis to detect biphasic reactions 1, 4
• Extended observation is indicated for patients with severe initial presentation or those requiring more than one dose of epinephrine 1
• Predictors of biphasic reactions include wide pulse pressure, unknown trigger, skin/mucosal symptoms, and drug triggers in children 1

Discharge Planning

• Prescribe two epinephrine autoinjectors before discharge (0.15 mg for patients 7.5-25 kg; 0.3 mg for patients 25-50 kg; 0.3-0.5 mg for adults) 1, 4
• Provide hands-on training and ensure the patient or caregiver can demonstrate proper autoinjector use 1, 8
• Arrange allergy/immunology referral for trigger identification and long-term management 9

Autoinjector Use in Community Settings

When to Use

• Administer immediately upon recognition of anaphylaxis symptoms, particularly respiratory (difficulty breathing, wheezing, throat tightness) or cardiovascular (hypotension, dizziness, syncope) manifestations 1, 2
• Use after known allergen exposure in patients with previous anaphylaxis, even if symptoms are initially mild 2
• When in doubt, err on the side of using the autoinjector—the risks of untreated anaphylaxis far outweigh the risks of appropriate epinephrine use 2, 7

Autoinjector Dosing

• Patients weighing 7.5-25 kg should receive the 0.15 mg dose 1
• Patients weighing ≥25 kg should receive the 0.3 mg dose 1
• Autoinjectors are preferred in community settings due to ease of use and accuracy compared to ampules and syringes 1