<prompt> Which of the following reduces the efficacy of oral contraceptives ?ErythromycinGriseofulvinCimetidineDisulfiram  <response>: 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 