Oxabolone is a synthetic anabolic steroid. It can be formulated as the cipionate ester prodrug oxabolone cipionate. Oxabolone cypionate is a structural derivative of nandrolone. It differs via the additional 4-hydroxyl group that is attached, therefore making oxabolone cypionate 4-hydroxynandrolone. Oxabolone is on the World Anti-Doping Agency's list of prohibited substances, and is therefore banned from use in most major sports. Oxabolone cypionate is a relatively rare drug that was once produced in Europe for human use. Was used for the treatment of osteoporosis. It is no longer produced by pharmaceutical companies; Upjohn and Pharmacia were the primary producers of it previously.