What medications are recommended for a patient being discharged after an anaphylactic reaction?

Anaphylaxis Discharge Medications

All patients discharged after anaphylaxis must receive an epinephrine auto-injector (two doses), along with a short course of H1 antihistamines, H2 antihistamines, and corticosteroids for 2-3 days, though evidence supporting adjunctive medications for preventing biphasic reactions is limited.

Essential Discharge Prescription: Epinephrine Auto-Injector

The single most critical discharge medication is an epinephrine auto-injector, which must be prescribed to every patient who has experienced anaphylaxis. 1

• Prescribe two doses of epinephrine auto-injector at discharge 1
• Dosing by weight:
  • 10-25 kg: 0.15 mg epinephrine auto-injector 1

  • 25 kg: 0.3 mg epinephrine auto-injector 1

• Patients must receive hands-on training in proper auto-injector use before discharge 1
• Establish a plan for monitoring expiration dates 1

Adjunctive Discharge Medications (2-3 Day Course)

While the 2020 JTFPP guidelines note that evidence for adjunctive medications preventing biphasic reactions is very low quality 1, the NIAID expert panel recommends continuation of the following after discharge 1:

H1 Antihistamine

• Diphenhydramine every 6 hours for 2-3 days 1
• Alternative: non-sedating second-generation antihistamine 1
• Dosing: 1-2 mg/kg per dose, maximum 50 mg 1

H2 Antihistamine

• Ranitidine twice daily for 2-3 days 1
• Dosing: 1-2 mg/kg per dose 1

Corticosteroid

• Prednisone daily for 2-3 days 1
• Dosing: 0.5 mg/kg for less critical episodes 1
• Adult dosing: equivalent to 1.0-2.0 mg/kg/day divided every 6 hours if severe 1

Important Caveats About Adjunctive Medications

The evidence supporting corticosteroids and antihistamines for preventing biphasic anaphylaxis is weak and contradictory. 1

• The 2020 JTFPP analysis found no clear evidence that glucocorticoids or antihistamines prevent biphasic reactions 1
• Some data suggest glucocorticoids may have a nonsignificant inverse trend with biphasic reactions in adults, but showed an opposite association in children (possibly confounded by severity) 1
• The Cross-Canada Anaphylaxis registry suggested antihistamines may provide benefit when used with epinephrine, but glucocorticoids with epinephrine resulted in worse outcomes 1
• The NIAID guidelines acknowledge that "little data support" the use of systemic corticosteroids for preventing biphasic or protracted reactions 1

Despite limited evidence, these medications are commonly prescribed based on expert consensus and theoretical benefit 1.

Additional Critical Discharge Components

Beyond medications, every discharged patient requires 1:

• Written anaphylaxis emergency action plan detailing trigger avoidance and early symptom recognition 1
• Medical identification jewelry or anaphylaxis wallet card 1
• Referral to allergist/immunologist for comprehensive evaluation and long-term management 1
• Education on biphasic reactions (can occur up to 72 hours later, typically around 8 hours) 1
• Follow-up appointment with primary care provider 1

Risk Stratification for Observation Period

Before discharge, patients should be observed for 4-6 hours minimum, with longer observation or admission for 1:

• Severe or refractory symptoms requiring multiple epinephrine doses 1
• History of biphasic reactions 1
• Coexisting severe asthma 1
• Cardiovascular disease or beta-blocker use 1
• Delayed epinephrine administration 1

In circumstances where epinephrine auto-injectors are not immediately available at discharge (e.g., pharmacy hours, cost barriers), clinical judgment regarding biphasic reaction risk and access to emergency care must guide discharge timing. 1