<prompt> Oral contraceptive failure occurs withCimetidineRifampicinMorphineEthanol  <response>: Rifampicin 1628 - Man Gillmann 741-KDT 6thCONTRACEPTION FAILURE - May occure if the following drugs are used concurrentlya Enzyme inducers - Phenytoin, Phenobarbitone, Primidone, Carbamazepine, Rifampicin, Rifabutinb Suppression of intestinal micro flora - Tetracyclines Ampicilline Doxycycilline 