This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti Microbial, Subject name: Pharmacology
Imipenem is combined with cilastatin to: 
Select and explain. 
A. Cilastatin prevents degradation of imipenem in kidney, B. Cilastatin inreases intestinal absorption of imipenem, C. Cilastatin inhibits beta lactamase activity, D. Both have synergistic activity against Pseudomonas
A: Cilastatin prevents degradation of imipenem in kidney
Answer: A: Cilastatin prevents degradation of imipenem in kidney 
Explanation: Ans. (A) Cilastatin prevents degradation of imipenem in kidney(Ref: Goodman and Gilman 13th/e p1035)Imipenem is rapidly inactivated by renal dehydropeptidase I, so it is combined with cilastatin, an inhibitor of this enzyme.Cilastatin increases the half life of imipenem and also inhibits the formation of nephrotoxic metabolite.Meropenem, doripenem and ertapenem are not metabolized by renal dehydropeptidase