Trenbolone undecanoate
Trenbolone undecanoate, or trenbolone undecylate, is a synthetic injected anabolic–androgenic steroid that is a derivative of nandrolone which was never marketed. It is the C17β undecanoate ester and a long-acting prodrug of trenbolone. The drug was described by researchers at Roussel Uclaf in 1967 and was the first long-lasting ester of trenbolone to be developed. Subsequently, trenbolone hexahydrobenzylcarbonate, a roughly equivalent compound, was developed and approved in Europe for human medical use in 1980, though it was discontinued in 1997. Trenbolone enanthate is another long-lasting ester of trenbolone. Similarly to trenbolone undecanoate, it was never approved for human use, but is sold on the black market for use by bodybuilders and athletes.