What are the appropriate take-home medications for patients with a history of allergic reactions?

Take-Home Medications for Patients with Allergic Reactions

All patients discharged after an allergic reaction must receive an epinephrine auto-injector (2 doses), oral prednisone 1 mg/kg daily (maximum 60-80 mg) for 2-3 days, an H1-antihistamine for 2-3 days, and an H2-antihistamine twice daily for 2-3 days. 1

Essential Discharge Medications

Epinephrine Auto-Injector (First-Line, Non-Negotiable)

Every patient with a history of anaphylaxis or at risk for severe reactions must be prescribed two epinephrine auto-injectors. 1

• Dosing by weight: 1, 2

  • Weight >25 kg: 0.3 mg epinephrine auto-injector
  • Weight 10-25 kg: 0.15 mg epinephrine auto-injector
  • Alternative dosing: 0.01 mg/kg IM (maximum 0.5 mg per dose)

• High-risk patients requiring auto-injectors include: 1

  • Previous systemic allergic reaction or anaphylaxis
  • Food allergy combined with asthma
  • Known allergy to peanut, tree nuts, fish, or crustacean shellfish
  • Consider for all patients with IgE-mediated food allergies

• Critical patient education points: 1

  • Inject into anterolateral thigh (never buttocks, digits, hands, or feet) 2
  • May repeat every 5-15 minutes if symptoms persist 1
  • Always carry both devices at all times
  • Demonstrate proper technique before discharge
  • Establish plan for monitoring expiration dates

Oral Corticosteroids (Adjunctive Therapy)

Prednisone 1 mg/kg daily (maximum 60-80 mg) for 2-3 days to prevent biphasic or protracted reactions. 1, 3, 4

• Alternative formulation: Methylprednisolone 1 mg/kg daily (maximum 60-80 mg) if oral prednisone not tolerated 1, 3

• Important caveats: 3, 4

  • Short 2-3 day courses do not require tapering
  • Evidence supporting corticosteroids for preventing biphasic reactions is limited, but this remains standard practice
  • Corticosteroids have no acute benefit (onset 4-6 hours) and should never replace epinephrine
  • Biphasic reactions occur in up to 20% of cases, all within 3 days

H1-Antihistamine (Adjunctive Therapy)

Diphenhydramine every 6 hours for 2-3 days, or alternatively a non-sedating second-generation antihistamine. 1, 5

• Dosing: 1-2 mg/kg per dose, maximum 50 mg 1
• Alternative: Less-sedating second-generation antihistamines (e.g., cetirizine) may be preferred to minimize sedation and anticholinergic effects 1, 5
• Oral liquid formulation absorbs more readily than tablets 1

H2-Antihistamine (Adjunctive Therapy)

Ranitidine twice daily for 2-3 days (or famotidine if ranitidine unavailable). 1, 3, 5

• Dosing: 1

  • Ranitidine: 1-2 mg/kg per dose, maximum 75-150 mg
  • Famotidine: 20 mg if ranitidine unavailable 3

• Rationale: Combination of H1 + H2 antihistamines provides superior symptom control compared to H1 alone 3, 5

Additional Discharge Requirements

Written Anaphylaxis Emergency Action Plan

Provide a detailed emergency action plan specifying: 1, 5

• Specific allergen(s) to avoid
• Early warning signs of anaphylaxis
• Step-by-step instructions for epinephrine administration
• When to call 911 (immediately after epinephrine use)
• Instructions to proceed to emergency facility even if symptoms improve

Follow-Up Arrangements

Schedule follow-up within 1-2 weeks with: 1, 4, 5

• Primary care physician for ongoing management
• Allergist referral for formal allergy testing, trigger identification, and consideration of immunotherapy if indicated

Critical Pitfalls to Avoid

Never prescribe antihistamines or corticosteroids alone without epinephrine auto-injectors — this is the most dangerous error and significantly increases risk of life-threatening progression. 4, 5

Never suggest antihistamines or corticosteroids can substitute for epinephrine — delayed epinephrine administration is implicated in anaphylaxis fatalities. 1, 4

Do not discharge patients prematurely — observe for minimum 4-6 hours after symptom resolution; longer observation (or admission) for severe reactions, multiple epinephrine doses, or patients with asthma. 1, 3

Ensure patients understand epinephrine is always first-line — antihistamines and corticosteroids are purely adjunctive and have no role in acute treatment. 3, 4, 5

Special Populations

Patients with Asthma

Asthmatic patients are at particularly high risk for fatal anaphylaxis and require heightened vigilance. 1, 5

• Poorly controlled asthma significantly increases anaphylaxis risk
• Wheezing in an asthmatic patient during allergic reaction mandates immediate epinephrine
• Consider higher corticosteroid doses (prednisolone 30-60 mg daily for 1-3 weeks) for asthma-related reactions 4

Patients on Beta-Blockers

Patients taking beta-blockers may have reduced response to epinephrine and require additional interventions. 3, 5

• Consider prescribing glucagon for home use in select cases (20-30 μg/kg for children, 1-5 mg for adults) 3, 5
• Educate that multiple epinephrine doses may be necessary
• Ensure close follow-up with cardiology and allergy specialists

Adolescents and Young Adults

This age group is at highest risk for life-threatening food-induced anaphylaxis, particularly from peanuts and tree nuts. 1

• Emphasize consistent carrying of auto-injectors
• Address risk-taking behaviors and peer pressure
• Reinforce that fatalities are associated with delayed or improper epinephrine dosing