What medication is used to treat anaphylaxis?

Epinephrine is the First-Line Medication for Anaphylaxis

Epinephrine is the only appropriate first-line medication for treating anaphylaxis and should be administered immediately when anaphylaxis is suspected. 1, 2, 3

Mechanism of Action

Epinephrine works through multiple mechanisms to reverse anaphylaxis:

• Alpha-1 adrenergic effects: Increases vasoconstriction and peripheral vascular resistance, decreases mucosal edema 2
• Beta-1 adrenergic effects: Increases cardiac inotropy and chronotropy 2
• Beta-2 adrenergic effects: Causes bronchodilation and decreases mediator release from mast cells and basophils 2, 3

Administration and Dosing

Recommended Route and Dosing

• Intramuscular (IM) injection in the mid-outer thigh (vastus lateralis muscle) is the preferred route 1, 2
• Adult dose: 0.3-0.5 mg of 1:1000 concentration IM 2
• Pediatric dose: 0.01 mg/kg of 1:1000 concentration IM (maximum 0.3 mg in prepubertal children and up to 0.5 mg in teenagers) 1, 2
• Epinephrine autoinjector dosing:
  • 0.15 mg for children weighing 7.5-25 kg
  • 0.3 mg for individuals weighing ≥25 kg 1, 2

Timing and Repeat Dosing

• Administer as soon as anaphylaxis is recognized 1, 4
• If symptoms persist, repeat dose every 5-15 minutes 2
• Approximately 6-19% of pediatric patients require a second dose 1

Why Epinephrine Over Other Medications

Epinephrine is superior to other medications for anaphylaxis because:

1. Rapid onset of action: IM epinephrine reaches peak plasma concentrations in approximately 8 minutes, compared to 34 minutes with subcutaneous injection 2

2. Comprehensive symptom relief: Epinephrine addresses all major anaphylactic symptoms including respiratory distress, hypotension, and shock 5

3. Life-saving effects: It is the only medication shown to prevent progression to fatal anaphylaxis 6

4. Antihistamines are inadequate: They do not relieve or prevent serious complications such as airway obstruction, hypotension, and shock. They also have a delayed onset (1-3 hours vs. <10 minutes for epinephrine) 5

Common Pitfalls to Avoid

• Delaying epinephrine administration: This is associated with increased mortality 2
• Using antihistamines as first-line treatment: Antihistamines do not address the life-threatening aspects of anaphylaxis 2, 5
• Withholding epinephrine due to unfounded concerns: The benefits of appropriately dosed epinephrine far outweigh the risks 6
• Subcutaneous administration: IM administration provides faster absorption and is more effective 2

High-Risk Patients

Certain populations require special attention:

• Patients with asthma: Higher risk for fatal anaphylaxis 2
• Adolescents: Also at higher risk for fatal anaphylaxis 2
• Patients with previous severe reactions: May require more aggressive treatment 2

Follow-Up Care

• Observe patients until symptoms fully resolve (typically 4-6 hours) 2
• Prescribe epinephrine autoinjectors upon discharge 2
• Refer to an allergist/immunologist 2
• Educate on trigger avoidance and proper use of emergency medications 2

Epinephrine remains universally recommended as the cornerstone of anaphylaxis management, with no absolute contraindications when treating this potentially life-threatening condition 1, 2, 6.