This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
All of the following drugs undergo hepatic metabolism before excretion, EXCEPT: 
Select and explain. 
A. Phenytoin, B. Diazepam, C. Penicillin G, D. Cimetidine
C: Penicillin G
Answer: C: Penicillin G 
Explanation: The pharmacokinetics of Penicillin G is dominated by very rapid renal excretion. About 10% of the drug is eliminated by glomerular filtration and rest by tubular secretion. The plasma t1/2 of penicillin G in healthy adults is 30 minutes. Ref: Essentials of Medical Pharmacology By K D Tripathi, 5th Edition, Pages 364, 372, 589, 655