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
Which of the following statement about Phenytoin is true? 
Select and explain. 
A. It follows zero order kinetics, B. It is not teratogenic, C. It is excreted unchanged in urine, D. It does not induce microsomal enzymes
A: It follows zero order kinetics
Answer: A: It follows zero order kinetics 
Explanation: Phenytoin follows zero order kinetics at therapeutic plasma concentration. Other drugs following zero order kinetics are warfarin, alcohol, aspirin, theophylline, and tolbutamide. *Phenytoin is a powerful microsomal enzyme inducer. *Phenytoin is metabolized to inactive products by liver. *Use of Phenytoin during pregnancy can cause Fetal hydantoin syndrome characterized by hypoplastic phalanges, cleft lip, cleft palate and microcephaly. It occurs due to a metabolite of phenytoin, arene oxide. REF: KATZUNG 14TH ED.