What is the treatment for an allergic reaction to antibiotics?

Treatment for Allergic Reactions to Antibiotics

The first-line treatment for antibiotic allergic reactions is to immediately discontinue the culprit antibiotic and administer epinephrine intramuscularly for severe reactions (anaphylaxis), followed by antihistamines and glucocorticoids based on reaction severity. 1, 2

Classification of Antibiotic Allergic Reactions

Antibiotic allergic reactions can be categorized into two main types:

Immediate-Type Reactions

• Occur within minutes to hours after antibiotic administration 3
• IgE-mediated (Type I hypersensitivity) 4
• Clinical manifestations include urticaria, angioedema, bronchospasm, hypotension, and anaphylaxis 1

Delayed-Type Reactions

• Occur hours to days after antibiotic administration 3
• Non-IgE mediated (typically Type IV hypersensitivity) 4
• Clinical manifestations include maculopapular rashes, fixed drug eruptions, and in severe cases, SCAR (Severe Cutaneous Adverse Reactions) 3

Management Algorithm

For Severe Immediate Reactions (Anaphylaxis)

1. Immediately discontinue the culprit antibiotic 3
2. Administer epinephrine 0.3-0.5 mg IM (1:1000 solution) for adults; may repeat every 5-15 minutes if needed 1
3. Establish and maintain airway if respiratory symptoms are present 1
4. Administer oxygen if hypoxemia is present 5
5. Provide IV fluid resuscitation for hypotension 5
6. Administer H1 antihistamines (e.g., diphenhydramine 25-50 mg IV/IM) to reduce urticaria and pruritus 5
7. Administer H2 blockers (e.g., ranitidine) as adjunctive therapy 5
8. Consider corticosteroids (e.g., methylprednisolone 125 mg IV) to prevent biphasic reactions 5

For Non-Severe Immediate Reactions

1. Discontinue the culprit antibiotic 3
2. Administer H1 antihistamines for symptomatic relief 5
3. Consider short course of oral corticosteroids if symptoms persist 5

For Delayed-Type Reactions

1. Discontinue the culprit antibiotic 3
2. For non-severe reactions: Symptomatic treatment with antihistamines and topical corticosteroids 3
3. For severe reactions (SCAR): Immediate hospitalization, supportive care, and systemic corticosteroids 3

Alternative Antibiotic Selection

After treating the allergic reaction, selecting an alternative antibiotic depends on the type of reaction and the antibiotic class involved:

For Beta-Lactam Allergies (Penicillins, Cephalosporins)

• For non-severe delayed-type reactions:

  • Avoid the culprit antibiotic 3
  • Avoid antibiotics with similar side chains 3
  • Other beta-lactams with dissimilar side chains can be used 3

• For severe delayed-type reactions:

  • Avoid all beta-lactam antibiotics 3
  • Consider consultation with a multidisciplinary team if beta-lactams are essential 3

• For immediate-type reactions:

  • Avoid the culprit antibiotic 3
  • For penicillin allergy, cephalosporins with dissimilar side chains can be used 3
  • For cephalosporin allergy, penicillins with dissimilar side chains can be used 3

For Non-Beta-Lactam Antibiotic Allergies

• For non-severe reactions:

  • The culprit antibiotic and others in the same class can be given in a controlled setting 3

• For severe reactions:

  • Avoid the culprit antibiotic and all others in the same class 3

Special Considerations

• Cross-reactivity: Certain antibiotics share structural similarities that increase cross-reactivity risk. For example, ceftazidime, cefiderocol, and aztreonam share an identical side chain 3

• Desensitization: For patients with life-threatening infections requiring treatment with an antibiotic to which they are allergic, desensitization protocols can be considered under specialist supervision 6

• Documentation: Clearly document the nature of the allergic reaction, including timing, symptoms, and severity, to guide future antibiotic selection 3

• Allergy testing: Consider referral for formal allergy testing after the acute phase to confirm the allergy and guide future antibiotic use 3

Common Pitfalls to Avoid

• Mislabeling non-allergic adverse reactions as allergies, which unnecessarily restricts antibiotic options 7

• Failing to distinguish between immediate and delayed-type reactions, which affects management decisions 3

• Assuming cross-reactivity between all antibiotics in a class without considering side chain similarities 3

• Delaying epinephrine administration in anaphylaxis, which increases mortality risk 1

• Not considering desensitization for patients with life-threatening infections requiring the culprit antibiotic 6