Should adrenaline (epinephrine) be administered during the early stages of an allergic reaction to intravenous (IV) antibiotics or only after anaphylaxis occurs?

Adrenaline Should Be Administered at the Early Stage of Allergic Reaction to IV Antibiotics

Adrenaline should be administered as soon as allergic symptoms to IV antibiotics are recognized, without waiting for full anaphylaxis to develop, as early intervention prevents progression to life-threatening anaphylaxis and improves outcomes. 1

Recognition of Allergic Reactions to IV Antibiotics

Allergic reactions to IV antibiotics can be classified by severity:

• Grade I: Cutaneous signs only (flushing, urticaria, angioedema)
• Grade II: Moderate multi-organ involvement (hypotension, tachycardia, bronchospasm)
• Grade III: Life-threatening hypotension or severe bronchospasm
• Grade IV: Cardiac or respiratory arrest

Early signs of allergic reactions may include:

• Cutaneous flushing, rash, or urticaria
• Angioedema
• Early respiratory symptoms (wheezing, difficulty breathing)
• Hypotension
• Tachycardia (or bradycardia in ~10% of cases) 2

Immediate Management Algorithm

1. Stop the offending IV antibiotic immediately
2. Administer adrenaline at first signs of systemic allergic reaction:
   • Adults: 0.5 mg (0.5 mL of 1:1000 solution) IM into anterolateral thigh 2, 3
   • Children >30 kg: 0.3-0.5 mg IM
   • Children <30 kg: 0.01 mg/kg (up to 0.3 mg) IM 3
3. Call for help (resuscitation team in hospital, emergency services in community)
4. Position patient appropriately (supine with legs elevated if hypotensive) 2
5. Administer oxygen (100%) and maintain airway 2
6. Establish IV access if not already present
7. Administer fluid resuscitation: 0.5-1L crystalloid rapidly for hypotension 2

Rationale for Early Adrenaline Administration

The Anaesthesia guidelines clearly state that "adrenaline should be given as early as possible" in allergic reactions 2. This is because:

1. Allergic reactions to IV antibiotics can progress rapidly to life-threatening anaphylaxis within minutes
2. Delayed administration of adrenaline has been implicated in fatalities 2
3. There is "no absolute contraindication to epinephrine administration in anaphylaxis" 2

The British Journal of Anaesthesia guidelines emphasize that "initial management of anaphylaxis should follow the ABC approach. Adrenaline is the most effective drug in anaphylaxis and should be given as early as possible." 2

Secondary Management

After initial adrenaline and fluid resuscitation:

1. Repeat adrenaline every 5-15 minutes if needed 2, 3
2. Consider IV adrenaline (0.05-0.1 mg) if shock persists despite IM doses 2, 1
3. Administer antihistamines: Chlorphenamine 10 mg IV (adult dose) 2
4. Administer corticosteroids: Hydrocortisone 200 mg IV (adult dose) 2
5. Consider bronchodilators for persistent bronchospasm 2

Common Pitfalls to Avoid

1. Delaying adrenaline administration - waiting for full anaphylaxis to develop before giving adrenaline is dangerous and can lead to fatalities 2
2. Overreliance on antihistamines and corticosteroids - these are adjunctive treatments and should never replace adrenaline 2
3. Inadequate fluid resuscitation - essential to combat vasodilatation 2
4. Failure to monitor - all patients should be observed for at least 6 hours after treatment due to risk of biphasic reactions 2

Special Considerations

• For patients on beta-blockers with refractory hypotension, consider glucagon 1-2 mg IV 2
• For persistent hypotension, consider starting an adrenaline infusion (0.05-0.1 μg/kg/min) 2
• Obtain mast cell tryptase levels (ideally at 1-2 hours after reaction onset and again at 24 hours) to confirm diagnosis 2

The evidence overwhelmingly supports early administration of adrenaline at the first signs of allergic reaction to IV antibiotics, rather than waiting for full anaphylaxis to develop. This approach saves lives by preventing progression to severe, life-threatening anaphylaxis.