What is the treatment for a patient with a severe allergy?

Treatment of Severe Allergy (Anaphylaxis)

Intramuscular epinephrine is the only first-line treatment for severe allergic reactions (anaphylaxis) and must be administered immediately—there is no substitute. 1, 2

Immediate Management Algorithm

First-Line Treatment: Epinephrine

• Administer epinephrine 0.01 mg/kg IM (maximum 0.5 mg per dose) into the anterior-lateral thigh immediately upon recognition of anaphylaxis 2
• For patients >25 kg: use 0.3 mg epinephrine autoinjector 2
• For patients 10-25 kg: use 0.15 mg epinephrine autoinjector 2
• May repeat every 5-15 minutes if symptoms persist or progress 2
• Epinephrine acts rapidly to reverse nearly all symptoms of anaphylaxis and stabilizes mast cells 3

Critical Pitfall: Using antihistamines as primary treatment is the most common reason for not administering epinephrine and significantly increases risk of progression to life-threatening reactions 1, 2. Never delay epinephrine to give antihistamines. 2

Positioning and Supportive Care

• Place patient recumbent with lower extremities elevated if tolerated 2
• Administer supplemental oxygen 2
• Establish IV access for fluid resuscitation 1

Respiratory Support

• For persistent wheezing: albuterol nebulizer 1.5 mL (child) or 3 mL (adult) every 20 minutes or continuously as needed 2
• For patients with albuterol allergy: use ipratropium bromide as alternative bronchodilator 4

Second-Line Adjunctive Therapy

These medications should ONLY be given AFTER epinephrine, never as substitutes: 2, 5

H1 Antihistamines

• Diphenhydramine 1-2 mg/kg IV or oral (maximum 50 mg) 2
• Oral liquid formulation absorbs faster than tablets 2
• Relieves itching and urticaria but does NOT treat bronchospasm or hypotension 2, 5

H2 Antihistamines

• Ranitidine 1-2 mg/kg (maximum 75-150 mg) IV or oral 2
• Combination of H1 and H2 antihistamines works better than either alone 2

Corticosteroids

• Methylprednisolone 1 mg/kg IV (maximum 60-80 mg) OR prednisone 1 mg/kg oral (maximum 60-80 mg) 2, 6
• Used to prevent biphasic or protracted reactions, though evidence is limited 1
• Effects not apparent for 4-6 hours, but early administration hastens resolution 4

Management of Refractory Anaphylaxis

• Repeated doses of epinephrine, IV fluids, corticosteroids, and vasopressor agents may be needed 1
• Prompt transfer to intensive care unit for treatment and monitoring is essential 1
• For patients on beta-blockers with reduced epinephrine response: glucagon 20-30 μg/kg (children) or 1-5 mg (adults) 2

Observation Period

• Observe for 4-6 hours or longer based on severity of reaction 1
• Monitor for biphasic reactions, which can occur hours after initial resolution 1

Discharge Planning and Long-Term Management

Prescriptions at Discharge

• Prescribe TWO epinephrine autoinjectors with proper training on use 1, 2
• Continue diphenhydramine every 6 hours for 2-3 days 1, 2
• Continue H2 antihistamine (ranitidine) twice daily for 2-3 days 1, 2
• Continue prednisone daily for 2-3 days 1, 2, 6

Patient Education

• Provide written anaphylaxis emergency action plan 1, 7
• Train on early recognition of anaphylaxis signs and symptoms 1
• Educate on allergen avoidance strategies 1
• Recommend medical identification jewelry or anaphylaxis wallet card 1

Follow-Up

• Schedule follow-up with primary care provider and refer to allergist/immunologist 1, 2
• Allergist evaluation for trigger identification and consideration of immunotherapy if indicated 2, 5

Special Populations Requiring Heightened Vigilance

• Patients with asthma are at particularly high risk for fatal anaphylaxis 2
• Presence of wheezing in asthmatic patients having allergic reaction mandates immediate epinephrine 2
• Patients with cardiovascular disease, those on MAO inhibitors, tricyclic antidepressants, or stimulant medications require careful risk-benefit assessment, but epinephrine benefit usually outweighs risks 1
• There are no absolute contraindications to epinephrine use in anaphylaxis 1