The Kentucky Horse Racing Commission on Tuesday placed three drugs on its prohibited substances list following positive findings for two of the substances in horses that raced in the state this fall. The two positives were both reported to commission staff in September by the commission’s testing laboratory, one for cannabidiol, which is widely available and marketed as a pain reliever to humans, and the other for cardarine, a drug that was developed to prevent tumors but has now been repurposed among internet pharmacies as a purported stamina builder.