This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharmacokinetics, Subject name: Pharmacology
Which of the following causes OCP failure? 
Select and explain. 
A. Carbamazepine, B. Rifampicin, C. NSAIDS, D. Ethambutol
B: Rifampicin
Answer: B: Rifampicin 
Explanation: ANSWER: (B) RifampicinREF: KDT 7th ed p. 317Contraceptive failure of OCP can occur if concurrently used with followingEnzyme inducers:By increase metabolism of OCRSSuppression of microbial flora: interfere with enterohepatic circulation* Phenytoin* Phenobarbitone* Primidone* Carbamezapine* Rifampidn* Tetracyclines* Ampiciliins