Stanozolol, commonly sold under the name Winstrol (oral), Tenabol and Winstrol Depot (intramuscular), was developed by Winthrop Laboratories in 1962. It is a synthetic anabolic steroid

Anabolic steroid

Anabolic steroids, technically known as anabolic-androgen steroids or colloquially simply as "steroids", are drugs that mimic the effects of testosterone and dihydrotestosterone in the body. They increase protein synthesis within cells, which results in the buildup of cellular tissue ,...

 derived from testosterone

Testosterone

Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

, and has been approved by the FDA

Food and Drug Administration

The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

 for human use.

Unlike most injectable anabolic steroids, stanozolol is not esterified and is sold as an aqueous suspension, or in oral tablet form.