This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Pharmacology, Subject name: Pharmacology
All the following drugs undergo metabolism by acetylation EXCEPT 
Select and explain. 
A. INH, B. Hydralazine, C. Procainamide, D. phenytoin
D: phenytoin
Answer: D: phenytoin 
Explanation: Ans) d) (Phenytoin) Ref: KDT 6th ed pg25Compounds having amino or hydrazine residue are conjugated wiyh the help of acetyl Co enzyme - A which include drugs like sulphonamides, INH, PAS, hydralazine, clonazepam, procainamide Phenytoin is metabolised in liver by hydroxylation and glucoronide conjugation.