What are the rescue medications for anaphylaxis in the event of a reaction to immunotherapy (intramuscular immunoglobulin) injections?

Rescue Medications for Anaphylaxis During Immunotherapy Injections

Epinephrine (1:1000 dilution, 0.2-0.5 mL) is the first-line treatment for anaphylaxis during immunotherapy injections and should be administered immediately via intramuscular injection in the lateral thigh. 1 There are no contraindications to epinephrine administration in anaphylactic reactions, and delayed administration is associated with increased mortality.

Primary Rescue Medication Protocol

First-Line Treatment

• Epinephrine:
  • Dose: 0.2-0.5 mL of 1:1000 solution (0.01 mg/kg in children; maximum 0.3 mg) 1
  • Route: Intramuscular injection in the lateral thigh (preferred over subcutaneous) 1, 2
  • Frequency: Can be repeated every 5 minutes as needed 1
  • Indication: For any signs of anaphylaxis including respiratory distress, hypotension, or significant cutaneous symptoms 3

Second-Line Medications

After epinephrine administration, consider:

• Antihistamines (adjunctive therapy only, never as replacement for epinephrine):

  • H1 antagonists (e.g., diphenhydramine 50 mg IV/IM) 1, 4
  • H2 antagonists (e.g., ranitidine 50 mg IV) - work better together with H1 antagonists 1

• Corticosteroids (for potential late-phase reactions):

  • Methylprednisolone 1-2 mg/kg IV 1
  • Not effective for immediate symptoms but may prevent biphasic reactions 5

• Supplemental treatments:

  • Oxygen by mask for respiratory distress 1
  • IV fluids (normal saline) for hypotension 1
  • Inhaled beta-2 agonists for bronchospasm 1
  • Vasopressors for refractory hypotension 1

Required Emergency Equipment

Every facility administering immunotherapy must have immediate access to:

• Stethoscope and sphygmomanometer
• Tourniquets, syringes, needles, and IV catheters (14-18 gauge)
• Aqueous epinephrine HCL 1:1000 wt/vol
• Oxygen administration equipment
• IV fluid setup
• Injectable antihistamines (H1 and H2)
• Injectable corticosteroids
• Appropriate airway management equipment
• Glucagon kit (for patients on beta-blockers) 1

Clinical Management Algorithm

1. Recognition: Monitor for signs of anaphylaxis (flushing, urticaria, angioedema, respiratory distress, hypotension, gastrointestinal symptoms) 3

2. Immediate action:

   • Stop immunotherapy injection immediately
   • Position patient appropriately (sitting for respiratory distress)
   • Assess ABCs (Airway, Breathing, Circulation)

3. Treatment sequence:

   • Administer epinephrine IM immediately
   • Establish/maintain IV access
   • Administer oxygen if respiratory symptoms present
   • Give antihistamines and corticosteroids as secondary medications
   • Monitor vital signs continuously

4. Post-reaction management:

   • Observe patient for at least 4-12 hours due to risk of biphasic reactions 5
   • Evaluate immunotherapy dose and schedule before continuing 1
   • Consider reducing maintenance dose after severe reactions 1

Important Considerations and Pitfalls

• Critical pitfall: Delaying epinephrine administration is associated with increased mortality 1, 6
• Route matters: Intramuscular injection in the thigh produces higher and faster peak plasma concentrations than subcutaneous injection 1, 2
• Beta-blockers: Patients on beta-blockers may have more severe reactions and require glucagon if unresponsive to epinephrine 1
• Asthma caution: Patients with asthma are at higher risk for severe reactions; consider measuring peak flow before administering immunotherapy 1, 5
• Observation period: All patients should wait at least 30 minutes after immunotherapy injections, as most severe reactions develop within this timeframe 1
• Documentation: Record all reactions, interventions, and responses 7

By following this protocol and having appropriate rescue medications and equipment readily available, healthcare providers can effectively manage anaphylactic reactions to immunotherapy injections and reduce the risk of adverse outcomes.