A 42-year-old woman with a documented severe IgE-mediated reaction to penicillin requires intravenous therapy for multidrug-resistant Pseudomonas aeruginosa pneumonia. The safest beta-lactam choice is:
- A Piperacillin-tazobactam
- B Meropenem
- C Aztreonam ✓
- D Ceftazidime
Correct answer: C. Aztreonam
Explanation
Aztreonam is a monocyclic beta-lactam (monobactam) whose side chain shares no structural homology with penicillins, cephalosporins or carbapenems, so cross-reactivity in true IgE-mediated penicillin allergy is negligible. Its one documented exception is ceftazidime, because both share an identical side chain, which eliminates option D. Carbapenems carry a small but real cross-reactivity rate, and piperacillin is directly contraindicated in anaphylactic penicillin allergy.
Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.