<prompt> Which of the following reduces the efficacy of oral contraceptives -ErythromycinGriseofulvinCimetidineDisulfiram  <response>: Ans. is b i.e., Griseofulvin o Contraceptive failure may occur if the following drugs are given concurrently :aEnzyme inducer -Enhances the metabolism of estrogen progesterone.1. Phenytoin3. Carbamazepine5. Primidone2. Phenobarbitone4. Rifampicin6. GriseofulvinbSuppression of intestinal microflora - enterohepatic circulation.1. Tetracyclines 2. Ampicillin 