A 42-year-old woman with a documented history of anaphylaxis to penicillin develops a complicated intra-abdominal infection with Enterobacter cloacae. Which antibiotic can be safely administered despite her history?
- A Amoxicillin-clavulanate
- B Aztreonam ✓
- C Ceftriaxone
- D Piperacillin-tazobactam
Correct answer: B. Aztreonam
Explanation
Aztreonam is a monobactam active only against aerobic Gram-negative bacilli. Its monocyclic beta-lactam ring shares minimal structural homology with penicillins and cephalosporins, so cross-reactivity in IgE-mediated penicillin allergy is negligible. One caveat examined in India and abroad is shared side-chain reactivity with ceftazidime, whose aminothiazolyl oxime side chain resembles aztreonam's. Amoxicillin, piperacillin and third-generation cephalosporins all carry a real risk of cross-reaction in true anaphylactic penicillin allergy.
Reference: Katzung Basic and Clinical Pharmacology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.