Use of in vitro technologies to study phase II conjugation in equine sports drug surveillance.

Within equine drug surveillance, there is significant interest in analyzing intact phase II conjugates of drugs in urine, but progress has been limited by a lack of reference material. In this study, in vitro techniques using equine liver fractions were employed to produce glucuronide and sulfate conjugates of stanozolol, 16β-hydroxystanozolol and nandrolone, the glucuronide conjugate of morphine and the glutathione metabolite of chlordinitrobenzene for the first time in equine sports drug surveillance. The glucuronide conjugate of the synthetic progestagen altrenogest was also produced in vitro, removing the requirement for sample hydrolysis during routine urinalyses. These results highlight the potential of in vitro studies for the production of phase II reference material, allowing the development of assays based on intact conjugates.