Elimination kinetic of 17β-estradiol 3-benzoate and 17β-nandrolone laureate ester metabolites in calves’ urine

Efficient control of the illegal use of anabolic steroids must both take into account metabolic patterns and associated kinetics of elimination; in this context, an extensive animal experiment involving 24 calves and consisting of three administrations of 17β-estradiol 3-benzoate and 17β-nandrolone laureate esters was carried out over 50 days. Urine samples were regularly collected during the experiment from all treated and non-treated calves. For sample preparation, a single step high throughput protocol based on 96-well C18 SPE was developed and validated according to the European Decision 2002/657/EC requirements. Decision limits (CCα) for steroids were below 0.1 μg L−1, except for 19-norandrosterone (CCα = 0.7 μg L−1) and estrone (CCα = 0.3 μg L−1). Kinetics of elimination of the administered 17β-estradiol 3-benzoate and 17β-nandrolone laureate were established by monitoring 17β-estradiol, 17α-estradiol, estrone and 17β-nandrolone, 17α-nandrolone, 19-noretiocholanolone, 19-norandrostenedione, respectively. All animals demonstrated homogeneous patterns of elimination both from a qualitative (metabolite profile) and quantitative point of view (elimination kinetics in urine). Most abundant metabolites were 17α-estradiol and 17α-nandrolone (>20 and 2 mg L−1, respectively after 17β-estradiol 3-benzoate and 17β-nandrolone laureate administration) whereas 17β-estradiol, estrone, 17β-nandrolone, 19-noretiocholanolone and 19-norandrostenedione were found as secondary metabolites at concentration values up to the μg L−1 level. No significant difference was observed between male and female animals. The effect of several consecutive injections on elimination profiles was studied and revealed a tendency toward a decrease in the biotransformation of administered steroid 17β form.