<prompt> Oral contraceptive failure can occur with:KetoconazoleAminoglutethimidemetyraponeGlucocoicoids  <response>: Rifampicin is a Microsomal enzyme inducer. It enhances the metabolism of oral contraceptives and cause failure. other enzyme inducers are phenytoin, phenobarbitone, carbamezipine, smoking, st johns wa- they can also cause contraceptive failure REF.Essential of medical pharmacology K D TRIPATHI 6 Edition, Page No -741 