Question

Imipenem,a newer antibiotic with a broad antibacterial spectrum, is co administered with cilastatin. Which of the following is the best reason for the same?

• A. Combination of antibiotics is synergistic against Pseudomonas specie
• B. Cilastatin aids gastrointestinal absorption of active moiety, imipenem
• C. Cilastatin inhibits beta=lactamase enzyme destroying imipenem
• D. Cilastatin inhibits an enzyme in kidney destroying imipenem

Answer 1

The Correct Option is D

Step 1: Ask one question: what does cilastatin actually do? It is an enzyme inhibitor, not an antibiotic, so its job must be to protect its partner drug.
Step 2: Imipenem is hydrolyzed by dehydropeptidase-I sitting on the renal brush border, so given alone it is degraded fast and produces a nephrotoxic by-product. Cilastatin blocks that very enzyme, letting imipenem survive in the urinary tract and reach the bladder intact.
Step 3: Because cilastatin lacks antibacterial action, option a (synergy) fails; the pair is an intravenous preparation, so option b (oral absorption) is irrelevant; and cilastatin does not touch beta-lactamases, eliminating option c.
Step 4: The mechanism narrows to protection from a renal enzyme.
\[\boxed{\text{Cilastatin inhibits a kidney enzyme that destroys imipenem}}\]