Carbapenems are resistant to most beta-lactamases because of:
- A Trans-configured C5 hydroxyethyl side chain that sterically prevents hydrolysis ✓
- B Addition of clavulanic acid in the preparation
- C A bicyclic ring system with no beta-lactam ring
- D Intrinsic efflux pump inhibitor activity
Correct answer: A. Trans-configured C5 hydroxyethyl side chain that sterically prevents hydrolysis
Explanation
The unique trans-stereochemistry of the 6-α-hydroxyethyl side chain of carbapenems sterically hinders the active site of most beta-lactamases, preventing enzymatic hydrolysis of the beta-lactam ring. Clavulanic acid is a separate beta-lactamase inhibitor added to other penicillins, not carbapenems. Carbapenems do contain a beta-lactam ring; they are bicyclic but the second ring is five-membered (not thiazolidine).
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.