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

Anaphylaxis Discharge Medications

All patients discharged after anaphylaxis must receive two epinephrine auto-injectors with hands-on training, plus a 2-3 day course of oral corticosteroids, H1 antihistamines, and H2 antihistamines to reduce risk of biphasic reactions, despite limited evidence for the adjunctive medications. 1, 2

Essential Discharge Prescription: Epinephrine Auto-Injector

Every patient must leave with two doses of epinephrine auto-injector—this is non-negotiable. 1, 2

• Dosing: 0.15 mg for patients weighing 10-25 kg; 0.3 mg for patients weighing >25 kg 2
• Provide hands-on training before discharge on proper auto-injector technique 2
• Establish a monitoring plan for expiration dates (auto-injectors expire after 1 year) 1
• Instruct patients to check that the liquid remains clear and store at room temperature 1
• Consider setting up automated pharmacy reminders for renewal 1

Additional patients requiring epinephrine auto-injectors: those with prior systemic allergic reactions or food allergy with coexisting asthma 1

Adjunctive Discharge Medications (2-3 Day Course)

Despite weak evidence, guidelines recommend continuing adjunctive therapy to potentially prevent biphasic reactions, which can occur up to 72 hours post-event (typically around 8 hours). 1, 2

H1 Antihistamine

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

H2 Antihistamine

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

Corticosteroid

• Prednisone daily for 2-3 days 1
• Dosing: 0.5-1 mg/kg daily 3, 2

Critical caveat: The evidence supporting corticosteroids and antihistamines for preventing biphasic anaphylaxis is weak and contradictory. 2, 4 A 2020 analysis found no clear evidence that glucocorticoids or antihistamines prevent biphasic reactions. 2 However, these medications appear to reduce hospital length of stay without evidence of harm, justifying their continued use as adjunctive therapy. 4

Additional Critical Discharge Components

Written Anaphylaxis Emergency Action Plan

• Must include trigger avoidance strategies 1, 2
• Early symptom recognition guidance 1, 2
• Step-by-step instructions for epinephrine self-injection 1

Medical Identification

• Recommend medical identification jewelry or anaphylaxis wallet card 1, 2

Follow-Up Care

• Schedule follow-up with primary care provider 1
• Refer to allergist/immunologist for comprehensive evaluation and long-term management 1, 2
• This specialist referral is essential for identifying triggers and developing prevention strategies 1

Patient Education on Biphasic Reactions

• Educate that symptoms can recur up to 72 hours later, typically around 8 hours 2, 5
• Patients should remain within ready access of emergency care for 48 hours post-discharge 6

Observation Period Before Discharge

• Minimum 4-6 hours observation for most patients 1, 2
• Prolonged observation or hospital admission required for: 1, 2
  • Severe or refractory symptoms
  • History of biphasic reactions
  • Coexisting severe asthma
  • Underlying cardiovascular disease
  • Delayed epinephrine administration
  • Patients on beta-blockers (may require glucagon 1-5 mg IV if refractory to epinephrine) 3

Common Pitfalls to Avoid

• Never discharge without providing the actual auto-injector or ensuring immediate prescription fill 1
• Do not rely solely on antihistamines or corticosteroids—epinephrine is the only first-line treatment 3, 7
• Avoid discharging patients too early—biphasic reactions occur in approximately 20% of cases 6
• Do not forget hands-on training—prescription alone is insufficient 2