A 45-year-old woman with a documented severe IgE-mediated reaction to penicillin develops a serious infection with Pseudomonas aeruginosa. Which beta-lactam can be administered with minimal risk of cross-reactivity?
- A Amoxicillin-clavulanate
- B Aztreonam ✓
- C Ceftriaxone
- D Piperacillin-tazobactam
Correct answer: B. Aztreonam
Explanation
Aztreonam is a monobactam whose monocyclic ring shares little structural homology with penicillins and cephalosporins, so cross-reactivity in IgE-mediated penicillin allergy is minimal. The one important exception is ceftazidime, which shares an identical side chain with aztreonam and can cross-react. Options A and D are penicillins and are absolutely contraindicated. Third-generation cephalosporins carry a small but real cross-reactivity risk, whereas aztreonam is the standard safe choice for Gram-negative cover in penicillin-allergic patients.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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