This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
CYP 3A4 enzyme are affected by 
Select and explain. 
A. Fexofenadine, B. Phenytoin, C. Carbamazepine, D. Pencillin
B: Phenytoin
Answer: B: Phenytoin 
Explanation: CYP3A4 cary out biotransformation of large numberof drugs. The inhibition of this isoenayme by erythromycin, clarithromycin, ketoconazole, itraconazole etc is responsible for impoant drug interactions with terfenadine, astemizole and cisapride. Rifamps barbiturates and other anticonvulsants are impoant inducers. Ref-KDT 7/e p24