What is the immediate treatment for a Grade 2 allergic reaction in an inpatient?

Immediate Treatment for Grade 2 Allergic Reaction in an Inpatient

For a Grade 2 allergic reaction in an inpatient setting, stop or slow the infusion if drug-related, administer H1 antihistamines (diphenhydramine 1-2 mg/kg IV, max 50 mg) and H2 antihistamines (ranitidine 1-2 mg/kg IV, max 75-150 mg), provide symptomatic treatment including bronchodilators if needed, and closely monitor for progression to Grade 3 or higher severity that would require immediate epinephrine. 1

Understanding Grade 2 Reactions

Grade 2 reactions involve symptoms or signs affecting more than one organ system and represent moderate severity allergic reactions. 1 These may include:

• Generalized pruritus, urticaria, flushing, or sensation of heat 1
• Angioedema (not involving larynx, tongue, or uvula) 1
• Mild asthma symptoms (cough, wheezing, shortness of breath) that respond to inhaled bronchodilators 1
• Rhinitis, throat clearing, or conjunctival symptoms 1
• Nausea, metallic taste, or headache 1

Critical distinction: If lower respiratory symptoms do not respond to bronchodilators, or if there is laryngeal edema, hypotension, or respiratory failure, this escalates to Grade 3 or 4, requiring immediate epinephrine. 1

Immediate Management Algorithm

Step 1: Stop or Modify the Trigger

• If infusion-related: Stop or significantly slow the infusion rate immediately 1
• Remove or discontinue the offending agent if identifiable 1

Step 2: Administer First-Line Medications for Grade 2

H1 Antihistamine (Diphenhydramine):

• Dose: 1-2 mg/kg per dose IV or oral 1, 2
• Maximum dose: 50 mg 1, 2
• IV route preferred in inpatient setting for faster onset 3

H2 Antihistamine (Ranitidine or Famotidine):

• Ranitidine: 1-2 mg/kg per dose 1, 2
• Maximum dose: 75-150 mg IV or oral 1, 2
• The combination of H1 and H2 antihistamines works better than either alone 2

Step 3: Bronchodilator Therapy (If Respiratory Symptoms Present)

Albuterol administration: 1

• MDI: 4-8 puffs for children, 8 puffs for adults 1
• Nebulized solution: 1.5 mL for children, 3 mL for adults 1
• Administer every 20 minutes or continuously as needed 1

Step 4: Consider Corticosteroids

Methylprednisolone or Prednisone:

• Dose: 1 mg/kg 1, 2
• Maximum: 60-80 mg 1, 2
• Methylprednisolone IV or prednisone oral 1, 4
• Important caveat: Corticosteroids do not treat the acute phase but may prevent biphasic or protracted reactions 2, 5

Step 5: Monitoring and Observation

• Observe in monitored area for minimum 6 hours from onset of reaction 1
• Continuously assess for progression to Grade 3 or 4 severity 1
• Monitor vital signs, respiratory status, and skin findings 1

Critical Decision Point: When to Use Epinephrine

Epinephrine is NOT routinely indicated for Grade 2 reactions that remain stable. 1 However, you must immediately administer epinephrine if any of the following develop:

• Lower respiratory symptoms not responding to inhaled bronchodilators 1
• Laryngeal edema, tongue swelling, or uvular swelling 1
• Hypotension or cardiovascular symptoms 1
• Rapid progression of symptoms 1
• Any Grade 3 or 4 features 1

Epinephrine dosing if needed:

• 0.01 mg/kg of 1:1,000 solution IM 5
• Maximum 0.5 mg per dose 5
• Administer in anterolateral thigh 1

Common Pitfalls to Avoid

Never delay epinephrine if the reaction progresses. The most common error is using antihistamines as primary treatment when epinephrine is indicated, which significantly increases risk for life-threatening progression. 2, 6

Do not confuse Grade 2 with Grade 3. If asthma symptoms require more than bronchodilators or show incomplete response, this is Grade 3 requiring epinephrine. 1

First-generation antihistamines can exacerbate hypotension in hemodynamically unstable patients—use cautiously and monitor blood pressure. 5

Antihistamines have slower onset (1-3 hours to peak) compared to epinephrine (<10 minutes), making them inappropriate as sole therapy for progressive reactions. 6

Discharge Planning After Grade 2 Reaction

Continue adjunctive medications: 1, 2

• Diphenhydramine every 6 hours for 2-3 days 1, 2
• H2 antihistamine twice daily for 2-3 days 1
• Prednisone daily for 2-3 days 1, 2

Prescribe epinephrine auto-injector (2 doses) with proper training for any patient at risk of recurrent reactions. 1, 2

Provide education on allergen avoidance and arrange follow-up with primary care physician and consider allergy specialist referral. 1, 2