This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
All of the following statements about phenytoin are true except: 
Select and explain. 
A. It follows Saturation kinetics, B. Anti-seizure activity closely resembles plasma concentration, C. Does not depress CNS, D. Cerebellar degeneration occurs on long-term administration
D: Cerebellar degeneration occurs on long-term administration
Answer: D: Cerebellar degeneration occurs on long-term administration 
Explanation: Phenytoin is not a CNS depressant; some sedation occurs at therapeutic doses, but this does not increase fuher with dose; rather toxic doses produce excitement and muscular rigidity. REF: ESSENTIALS OF MEDICAL PHARMACOLOGY KD TRIPATHI 8TH ED.