## **Core Concept**
Cilastatin is a dehydropeptidase inhibitor used in combination with certain antibiotics to prevent their renal metabolism, thereby prolonging their antibacterial activity.

## **Why the Correct Answer is Right**
Cilastatin is specifically combined with **Imipenem**, a carbapenem antibiotic. Imipenem is metabolized by renal dehydropeptidase-1, which leads to its inactivation. By inhibiting this enzyme, cilastatin prevents the breakdown of imipenem, thus prolonging its effective duration of action and allowing it to achieve therapeutic levels in the body.

## **Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because there is no well-known combination of cilastatin with this antibiotic to prolong its duration of action.
* **Option B:** This option is incorrect as there is no established combination of cilastatin with this antibiotic for increasing its duration.
* **Option D:** This option is incorrect because, although meropenem is another carbapenem antibiotic like imipenem, cilastatin is not used with meropenem. Meropenem is less susceptible to dehydropeptidase-1 and does not require cilastatin.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the combination of **imipenem** and cilastatin is used to treat a wide range of bacterial infections. This combination is known as **Imipenem/Cilastatin** and is administered intravenously. It is effective against both Gram-positive and Gram-negative bacteria.

## **Correct Answer:** . Imipenem.