A 45-year-old woman with a post-neurosurgical brain abscess is treated with high-dose IV imipenem. She has concurrent renal impairment. Two days later she develops myoclonic jerks progressing to a generalized seizure. The feature of imipenem most responsible for this complication is:

• A Its strong induction of hepatic cytochrome enzymes
• B Its accumulation of the cilastatin component in the CSF
• C Its basic thienamycin side chain promoting GABA antagonism in the cortex ✓
• D Its high protein binding displacing endogenous ligands

Explanation

Imipenem lowers the seizure threshold by competitively inhibiting GABA binding at cortical receptors, attributed to the basicity of its B2 side chain. High doses, renal impairment with drug accumulation, and CNS lesions such as brain abscess are recognized risk factors, so dosing must be adjusted and the infusion slowed. Meropenem, whose side chain is modified, carries a substantially lower seizure risk and is preferred in CNS infection.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.