This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
CYP 3A4 enzymes are affected by: a) Fexofenadine b) Phenytoin c) Carbamazepine d) Azithromycin e) Penicillin 
Select and explain. 
A. ab, B. bc, C. ad, D. bd
B: bc
Answer: B: bc 
Explanation: CYP3A4 cary out biotransformation of large number of drugs. The inhibition of this isoenzyme by erythromycin, clarithromycin, ketoconazole, itraconazole etc. is responsible for important drug interactions with terfenadine, astemizole and cisapride. Rifampicin, barbiturates and other anticonvulsants are important inducers.