Nandrolone formate, also known as nandrolone carboxylate or nandrolone methanoate, as well as 19-nortestosterone 17ò-formate or estr-4-en-17ò-ol-3-one 17ò-formate, is a synthetic, injected anabolicâÂÂandrogenic steroid (AAS) and a derivative of 19-nortestosterone (nandrolone) that was never marketed. It is an androgen ester â specifically, the C17ò formate ester of nandrolone.