Degradation and transformation of 17α-trenbolone in aerobic water-sediment systems.

Synovex® ONE is an extended-release implant containing the active ingredients estradiol benzoate and trenbolone acetate for use in beef steers and heifers. Trenbolone acetate is rapidly hydrolyzed in cattle to form 17β-trenbolone and its isomer, 17α-trenbolone, which are further transformed to a secondary metabolite, trendione. As part of the environmental assessment for the use of Synovex ONE, data were generated to characterize the fate of 17α-trenbolone, which is the principal metabolite found in cattle excreta, in the environment. A study was conducted to determine the degradation and transformation of [ C]-17α-trenbolone in 2 representative water-sediment systems under aerobic conditions. The same transformation products, 17β-trenbolone and trendione, were formed, principally in the sediment phase, in both systems. From the production of these transformation products, the 50% disappearance time (DT50) values of 17β-trenbolone and trendione were determined, along with the DT50 values of the parent compound and the total drug (17α-trenbolone + 17β-trenbolone + trendione). The DT50 values for the total system (aqueous and sediment phase) and for the total residues (17α-trenbolone + 17β-trenbolone + trendione) in the 2 systems were 34.7 d and 53.3 d, respectively. Environ Toxicol Chem 2017;36:630-635. © 2016 SETAC.