Dimethisterone (brand name Secrosteron) is an orally active progestational agent. It was developed by the British pharmaceutical company British Drug Houses and was first reported in the literature in 1959 with introduction for medical use as Secrosteron. Relative to ethisterone, it is 12 times as potent orally as a progestogen in animals (Clauberg test). It has an oral LD50 in mice of 7.65 g/kg, no apparent anabolic, androgenic properties and no significant effect on sodium, potassium or water excretion in saline loaded rats. Dimethisterone was introduced in the United States as an oral contraceptive for birth control in combination with ethinylestradiol under the brand name Oracon (25 mg dimethisterone, 100 ug ethinylestradiol) and was produced by Mead Johnson & Company (Evansville, Indiana) in 1974. This preparation was eventually found to be associated with a substantially increased risk of endometrial cancer in women, and is now no longer marketed.