## Core Concept
Imipenem is a carbapenem antibiotic that is effective against a wide range of bacteria. However, it is prone to degradation by the renal enzyme dehydropeptidase-1 (DHP-1). To overcome this issue, imipenem is combined with cilastatin.

## Why the Correct Answer is Right
Cilastatin is a specific inhibitor of dehydropeptidase-1 (DHP-1), an enzyme present in the renal tubules. When imipenem is administered alone, DHP-1 rapidly metabolizes it, leading to a loss of its antibacterial activity. By co-administering cilastatin, the degradation of imipenem is prevented, thereby maintaining its therapeutic efficacy and allowing it to reach the bloodstream and target sites in its active form.

## Why Each Wrong Option is Incorrect
* **Option A:** This option is incorrect because there is no well-known effect of cilastatin on liver enzymes that would be relevant to the combination with imipenem.
* **Option B:** This option is incorrect as there is no established role of cilastatin in enhancing the bactericidal activity of imipenem; its primary function is to protect imipenem from renal metabolism.
* **Option C:** This option is incorrect because while cilastatin does affect renal function by inhibiting DHP-1, its primary purpose in combination with imipenem is not to increase renal excretion of imipenem but to prevent its metabolism.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the combination of imipenem and cilastatin (marketed as Primaxin) is used to treat a variety of infections, including those caused by bacteria that are resistant to other antibiotics. This combination is particularly useful in severe infections where broad-spectrum coverage is essential.

## Correct Answer: D. prevent its degradation by renal enzymes.