An in vivo study was performed in order to evaluate the depletion time of stanozolol and its main metabolites using naturally incurred urine sample collected after the administration of intramuscular injections in 12 steers. A stability study was also carried out to investigate the influence of the storage period and the freeze-thaw cycles. A fast parent drug metabolization was observed, because within 6 h after drug administration, the signal of the metabolite 16β-hydroxystanozolol was predominant. After the second drug administration, a detection window of 17 days was obtained. The stability was studied using ANOVA, in which a storage condition of -20 °C proved stable during 240 days, which was also confirmed after 5 freeze-thaw cycles.
Keywords: 16-β-hydroxystanozolol; UHPLC-Q-Orbitrap; bovine urine; depletion; stability study; stanozolol.