<prompt> Which of the following drugs is an inhibitor of cytochrome p450 enzymes ?KetoconazoleRifampicinPhenytoinPhenobarbitone  <response>: - Cytochrome p450 enzymes are microsomal enzymes present on smooth endoplasmic reticulum.- Of the given options, only Ketoconazole is a microsomal enzyme inhibitor. Rest all are enzyme inducers. 