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
[{'content': 'Which of the following reduces the efficacy of oral contraceptives ? \nSelect and explain. \nA. Erythromycin, B. Griseofulvin, C. Cimetidine, D. Disulfiram', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Griseofulvin Contraceptive failure may occur if the following drugs are given concurrently : (a) Enzyme inducer Enhances the metabolism of estrogen & progesterone. Phenytoin 3. Carbamazepine 5. Primidone 2. Phenobarbitone 4. Rifampicin 6. Griseofulvin (b) Suppression of intestinal microflora enterohepatic circulation. 1. Tetracyclines 2. Ampicillin", 'role': 'assistant'}]