similar choleretic effects and a wider species distribution. However, CDCA is not as well-tolerated in humans and it does not show immunomodulating or chemoprotective effects. Both are 7-hydroxyl derivatives of deoxycholic acid, but UDCA has the group in the beta instead of the alpha orientation. Biosynthesis Among mammals, only bears (Ursidae; excluding giant pandas) produce UDCA at useful amounts (>30%). It is produced in the bear liver, but the pathway remains unknown. Other vertebrates produce UDCA in much smaller amounts by gut bacteria. CDCA is oxidized into 7-oxo-CDCA then reduced into UDCA. Industrial production UDCA is most commonly produced from cholic acid (CA) derived from bovine bile, a by-product of the beef industry. The current yield of this semisynthesis is about 30%. Society and culture Names The term is from the Latin noun ursus meaning bear, as bear bile contains the substance. Ursodeoxycholic acid can be chemically synthesized and is marketed under multiple trade names, including Ursetor, Udikast, Actibile, Actigall, Biliver, Deursil, Egyurso, Udcasid, Udiliv, Udinorm, Udoxyl, Urso, Urso Forte, Ursocol, Ursoliv, Ursofalk, Ursosan, Ursoserinox, Udimarin, Ursonova, and Stener. History Bear bile, a natural source of UDCA, is used in traditional Chinese medicine since the seventh century. Japanese scientists successfully synthesized UDCA chemically in 1955. The earliest reference to UDCA in PubMed dates to 1957 under an alternative spelling "ursodesoxycholic acid", in a small-scale clinical trial. Ursodeoxycholic acid (application filed by Allergan) was approved for use in the United States in December 1987, and was designated an orphan drug. References External links Ursodeoxycholic acid in the British National Formulary (BNF is only available in the UK) AbbVie brands Bile acids Cholanes Drugs acting on the gastrointestinal system and metabolism Orphan drugs