Anaphylaxis Clinical Pathway — Emergency Department

Adjunctive Medications

Antihistamines (H1) relieve the symptoms, hives/itch, but do not relieve severe symptoms.
Addition of antihistamine (H2) may provide more symptomatic relief for pruritis and abdominal symptoms.

Medication Route mg/kg Max Dose Comments
Diphenhydramine IV/PO 1 50 mg  
Cetirizine PO   10 mg
6-23 months
2-5 years
> 6 years
2.5 mg/day
2.5-5 mg/day
5-10 mg/day
Famotidine IV
20 mg
40 mg
Administer IV over 2 minutes


For patients who respond well to epinephrine, the addition of steroids may not be necessary unless used to treat airway or respiratory disease. There is some thought that it may decrease the risk of biphasic reactions; however a 2020 systematic review failed to document a benefit.


  • Anaphylaxis-a 2020 practice parameter update, systematic review, and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) analysis.
Medication Route mg/kg Max Dose Comments
Methylprednisolone IV 2 125 mg  
Prednisone PO 2 60 mg  
Dexamethasone PO 0.6 8 mg Prednisone alternative
No second dose required