Imipenem, a newer antibiotic with a broad antibacterial spectrum, is coadministered with cilastin because –
**Core Concept**
Imipenem is a carbapenem antibiotic with a broad spectrum of activity against both Gram-positive and Gram-negative bacteria. However, it is highly susceptible to degradation by renal dehydropeptidase I, an enzyme present in the renal tubules.
**Why the Correct Answer is Right**
Cilastatin, a dehydropeptidase inhibitor, is coadministered with imipenem to prevent its degradation by renal dehydropeptidase I. This allows imipenem to be excreted intact in the urine, thereby maintaining its antibacterial activity. By inhibiting the enzyme responsible for degrading imipenem, cilastatin enhances the efficacy of imipenem and prevents the development of resistance.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because cilastatin does not have any direct effect on the absorption or distribution of imipenem.
**Option B:** This option is incorrect because cilastatin does not have any effect on the metabolism of imipenem via the liver.
**Option C:** This option is incorrect because cilastatin does not have any direct effect on the mechanism of action of imipenem.
**Clinical Pearl / High-Yield Fact**
Cilastatin is a valuable example of a pharmacological agent that can be used to optimize the efficacy of another drug by inhibiting an enzyme that degrades it.
**Correct Answer: C. Cilastatin prevents the degradation of imipenem by renal dehydropeptidase I.**