**Question:** Cilastatin is given along with:

Cilastatin is an antibiotic used in combination with imipenem, which is a carbapenem antibiotic. The correct answer is:

**Correct Answer:** B. Imipenem

**Core Concept:** Cilastatin and imipenem are part of a class of antibiotics called carbapenems, which are used to treat serious infections caused by bacteria.

**Why the Correct Answer is Right:** Cilastatin is an enzyme inhibitor that prevents the degradation of imipenem by dehydropeptidase-1, an enzyme present in the renal tubule of the kidney. This allows imipenem to be more effectively excreted in urine and maintain its therapeutic levels in the body. By inhibiting dehydropeptidase-1, cilastatin enhances the activity of imipenem, making it a crucial component for its effective utilization.

**Why Each Wrong Option is Incorrect:**

**A.** Cilastatin is not an antibiotic and does not directly contribute to the antimicrobial effect of imipenem. This option is incorrect because cilastatin's role is solely to protect imipenem from degradation, not to treat the infection itself.

**C.** Cilastatin is a dipeptidase inhibitor, which is another type of enzyme inhibitor used for different purposes (e.g., in immunosuppressive therapy after organ transplantation). While dipeptidase inhibitors do exist, cilastatin is specifically designed for its role in enhancing the activity of imipenem.

**D.** Cilastatin is not an antibiotic but an enzyme inhibitor, so it cannot directly combat infections. This option is incorrect because cilastatin's function is to protect imipenem, not to treat infections.

**Why the Correct Answer is Right:**

Imipenem is a carbapenem antibiotic that is effective against a broad spectrum of gram-negative and gram-positive bacteria. In combination with cilastatin, imipenem exhibits enhanced antimicrobial activity and is used for the treatment of serious infections. Cilastatin's role is to protect imipenem from degradation, ensuring its stability and therapeutic effectiveness.

**Clinical Pearl:** The combination of imipenem and cilastatin, marketed as Imipenem-cilastatin, is a commonly used antibiotic regimen for treating various bacterial infections, particularly in critically ill patients or those with compromised renal function. This combination ensures that imipenem reaches optimal concentrations in the body to effectively combat infections while minimizing potential side effects related to high serum levels of imipenem.