This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal tract, Subject name: Pharmacology
cimetidine inhibits the metabolism of all the following drugs except: 
Select and explain. 
A. phenytoin, B. warfarin, C. ketoconazole, D. diazepam
C: ketoconazole
Answer: C: ketoconazole 
Explanation: cimetidine is a potent inhibitor of.microsomal enzymes.it prolongs the half life of warfarin, theophyllin ,phenytoin,oral hypoglycemic agents ,alcohol and benzidiazepines.(ref KDT 6/e p630)