This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pharmacology
[{'content': 'Oral contraceptive failure occurs with \nSelect and explain. \nA. Cimetidine, B. Rifampicin, C. Morphine, D. Ethanol', 'role': 'user'}, {'content': 'Answer: B \nExplanation: (Rifampicin) (1628 - Man & Gillmann) (741-KDT 6th)CONTRACEPTION FAILURE - May occure if the following drugs are used concurrently(a) Enzyme inducers - Phenytoin, Phenobarbitone, Primidone, Carbamazepine, Rifampicin, Rifabutin(b) Suppression of intestinal micro flora - Tetracyclines Ampicilline Doxycycilline', 'role': 'assistant'}]