<prompt> All the following drugs undergo metabolism by acetylation EXCEPTINHHydralazineProcainamidephenytoin  <response>: 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. 