What is the treatment for extreme hypersensitivity?

Treatment of Extreme Hypersensitivity Reactions

For extreme hypersensitivity reactions, immediate administration of epinephrine is the first-line treatment, followed by antihistamines, corticosteroids, and supportive care based on symptom severity. 1

Initial Management of Anaphylaxis (Most Severe Form of Hypersensitivity)

First-Line Treatment

• Administer epinephrine immediately upon recognition of anaphylaxis:
  • Adults: 0.3-0.5 mg of 1:1000 (1 mg/mL) solution intramuscularly into the vastus lateralis (anterolateral thigh)
  • Children: 0.01 mg/kg (maximum 0.3 mg) of 1:1000 solution 1
• Repeat epinephrine every 5-15 minutes if symptoms persist 1
• Activate emergency medical services immediately 1

Patient Positioning

• Place patient in recumbent position with legs elevated if tolerated
• Allow sitting up if respiratory distress predominates
• For pregnant patients, position with left uterine displacement 1

Fluid Resuscitation

• Administer IV crystalloids (normal saline) for hypotension:
  • Adults: 500-1000 mL rapid bolus
  • Children: 20 mL/kg, repeated as needed 1

Adjunctive Medications

Antihistamines (after epinephrine)

• H₁ antihistamines: Diphenhydramine 1-2 mg/kg (max 50 mg) IV/IM/PO 1, 2
• H₂ antihistamines: Ranitidine twice daily for 2-3 days 1
  • Combination of H1 and H2 blockers shows synergistic effects in controlling hypersensitivity reactions 3

Corticosteroids

• Administer after epinephrine:
  • Prednisone 0.5-1 mg/kg or methylprednisolone 1
  • For severe reactions, corticosteroids may help prevent prolonged or biphasic reactions 4

Additional Interventions

• For patients on beta-blockers with poor response to epinephrine: Consider IV glucagon 1-2 mg 1
• For bronchospasm: Inhaled beta-2 agonists (albuterol) 1

Management Based on Severity and Type

Mild to Moderate Reactions

• For isolated skin manifestations (urticaria, pruritus):
  • Antihistamines may be sufficient
  • Monitor closely for progression 4

Severe Reactions (including anaphylaxis)

• Follow anaphylaxis protocol with epinephrine as first-line treatment
• Monitor for at least 4-6 hours after symptom resolution for biphasic reactions 1

Drug-Specific Hypersensitivity Management

Platinum Agent Reactions

For platinum-based chemotherapy reactions 4:

1. First exposure (platinum naive):

   • Decrease infusion rate
   • Stop infusion if symptoms occur
   • Administer antihistamine
   • If vital signs remain stable, rechallenge with premedication (antihistamines, corticosteroids, H2 blockers)
   • Consider allergist consultation

2. Second or further exposure:

   • Administer antihistamine for symptoms
   • Corticosteroid ± IM epinephrine if symptoms persist
   • Do not rechallenge until evaluated by allergist
   • Consider desensitization with specialized expertise

3. Severe reactions (shortness of breath, blood pressure changes, dyspnea, GI symptoms):

   • Follow anaphylaxis protocol
   • Do not rechallenge without desensitization protocol

Desensitization for Required Medications

When a medication causing hypersensitivity is essential for treatment 5, 6:

1. Evaluate necessity of the medication and potential alternatives
2. Consult with allergist for appropriate desensitization protocol
3. Desensitization procedure:
   • Performed under medical supervision with emergency equipment available
   • Involves administering gradually increasing doses starting with extremely small amounts
   • Typically requires 4-12 hours depending on protocol
   • Success rates of 90% or higher have been reported for chemotherapy agents 6

Post-Treatment Care

• Prescribe epinephrine autoinjector (2 doses) for patients with history of anaphylaxis
• Provide an emergency action plan
• Arrange follow-up with an allergist-immunologist
• Educate on trigger avoidance and recognition of early symptoms 1

Important Considerations

• Delaying epinephrine administration is the most dangerous error in managing severe hypersensitivity reactions 1
• Antihistamines should never replace epinephrine as first-line treatment for anaphylaxis
• There are no absolute contraindications to epinephrine use in anaphylaxis; benefits outweigh risks even in patients with cardiovascular disease 1
• Patients with history of mild reactions can progress to severe reactions upon re-exposure 4
• For patients with history of antihistamine hypersensitivity (rare but reported), alternative antihistamine preparations from different chemical classes may be tolerated 7

By following this systematic approach to extreme hypersensitivity management, prioritizing epinephrine for severe reactions, and utilizing appropriate adjunctive therapies, most hypersensitivity reactions can be effectively controlled while minimizing morbidity and mortality.