What is the treatment for an allergic reaction to intravenous (IV) antibiotics, specifically the administration of intramuscular (IM) adrenaline (epinephrine)?

Management of Allergic Reactions to IV Antibiotics with Intramuscular Epinephrine

Intramuscular epinephrine is the first-line treatment for anaphylaxis due to IV antibiotics and should be administered immediately when signs of anaphylaxis are recognized. 1

Immediate Management Protocol

1. Stop the antibiotic infusion immediately

2. Administer epinephrine intramuscularly into the anterolateral thigh:

   • Adults and children ≥30 kg: 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) 2
   • Children <30 kg: 0.01 mg/kg (0.01 mL/kg of 1:1000 solution), maximum 0.3 mg 2

3. Position the patient appropriately:

   • Supine with legs elevated for hypotension
   • Sitting position if respiratory distress is predominant 1

4. Maintain IV access and administer oxygen if respiratory symptoms are present 1

5. Repeat epinephrine every 5-10 minutes as necessary if symptoms persist 3, 2

   • The 5-minute interval can be shortened if clinically indicated 3

Secondary Management

After initial epinephrine administration:

1. Administer IV fluids:

   • Normal saline 1-2 L (20-30 mL/kg) as rapid bolus for hypotension 3, 1
   • Repeat fluid boluses if inadequate response

2. Consider adjunctive medications (after adequate epinephrine and fluid resuscitation):

   • Chlorphenamine (H1 antihistamine): 10 mg IV for adults 3
   • Hydrocortisone: 200 mg IV for adults 3
   • For persistent bronchospasm: nebulized salbutamol/albuterol 1

Management of Refractory Reactions

If inadequate response after 10 minutes:

1. Escalate epinephrine dosing:

   • Double the bolus dose 3
   • Consider epinephrine infusion (0.05-0.1 μg/kg/min) 3

2. For persistent hypotension:

   • Add vasopressor infusion (norepinephrine, phenylephrine) 3
   • Consider glucagon (1-2 mg IV) if patient is on beta-blockers 3, 1

Grading of Reactions and Response

The management approach should be tailored to the severity of the reaction:

• Grade I: Cutaneous signs only - monitor closely
• Grade II: Moderate symptoms - epinephrine + fluids
• Grade III/IV: Severe symptoms/anaphylaxis - aggressive management with epinephrine, fluids, and additional measures 1

Monitoring and Observation

• Monitor vital signs continuously until resolution
• Observe for at least 6 hours after stabilization 3
• For severe reactions, consider observation for 24 hours due to risk of biphasic reactions 1

Common Pitfalls to Avoid

1. Delayed administration of epinephrine - this is the most common cause of fatal anaphylaxis 1, 4
2. Using subcutaneous instead of intramuscular epinephrine - IM administration in the thigh provides faster and higher plasma levels 3
3. Relying solely on antihistamines - these are adjunctive treatments only and do not replace epinephrine 1
4. Mistaking anaphylaxis for vasovagal syncope - anaphylaxis typically presents with multiple system involvement 1

Evidence Quality and Considerations

The recommendation for IM epinephrine as first-line treatment is supported by multiple high-quality guidelines 3. While no randomized controlled trials exist on epinephrine's efficacy in anaphylaxis (due to ethical constraints), observational data strongly support its use 5.

The American Heart Association and American Red Cross (2024) provide Class 1 recommendations (strongest) for epinephrine administration in anaphylaxis 3, and the FDA label specifically indicates epinephrine for emergency treatment of allergic reactions including anaphylaxis 2.

Most anaphylaxis cases (approximately 90%) respond to a single dose of epinephrine 6, but having the ability to administer additional doses is crucial for severe or refractory reactions.