<prompt> Which does not effect metabolism of oral contraceptive pill ?PhenytoinGresiofulvinPrimidonePenicillin  <response>: Ans. is d i.e., Penicillin Contraceptive failure may occur if the following drugs are given concurrently : a Enzyme inducer - Enhances the metabolism of estrogen progesterone. Phenytoin Carbamazepine Primidone Phenobarbitone Rifampicin Griseofulvin b Suppression of intestinal microflora - enterohepatic circulation. Tetracyclines Ampicillin 