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Samples of the "dietary supplement" Furazadrol sourced through the internet have been reported to contain the designer anabolic androgenic steroids [1',2']isoxazolo[4',5':2,3]-5α-androstan-17β-ol (furazadrol F) and [1',2']isoxazolo[4',3':2,3]-5α-androstan-17β-ol (isofurazadrol IF). These steroids contain an isoxazole fused to the A-ring and were designed to offer anabolic activity while evading detection, raising concerns over the potential for abuse of this preparation in sports. The metabolism of Furazadrol (F:IF, 10:1) was studied by in vivo methods in greyhounds. Urinary phase II Furazadrol metabolites were detected as glucuronides after a controlled administration. These phase II metabolites were subjected to enzymatic hydrolysis by Escherichia coli β-glucuronidase to afford the corresponding phase I metabolites. Using a library of synthetically-derived reference materials, the identities of seven urinary Furazadrol metabolites were confirmed. Major confirmed metabolites were isofurazadrol IF, 4α-hydroxyfurazadrol 4α-HF, and 16α-hydroxy oxidised furazadrol 16α-HOF, while the minor confirmed metabolites were furazadrol F, 4β-hydroxyfurazadrol 4β-HF, 16β-hydroxyfurazadrol 16β-HF, and 16β-hydroxy oxidised furazadrol 16β-HOF. One major hydroxyfurazadrol and two dihydroxyfurazadrol metabolites remained unidentified. Qualitative excretion profiles, limits of detection, and extraction recoveries were established for furazadrol F and major confirmed metabolites. These investigations identify the key urinary metabolites of Furazadrol following oral administration, which can be incorporated into routine screening by anti-doping laboratories to aid the regulation of greyhound racing.

Dexamethasone, formulated as sodium phosphate and as phenylpropionate combined with sodium phosphate, was administered subcutaneously to six greyhounds. Plasma and urine were collected for up to 240 h and analysed with a limit of quantification (LOQ) of at least 100 pg/ml for dexamethasone. Dexamethasone, formulated as sodium phosphate, terminal half-life was 10.4 h in plasma and approximately 16 h in urine, and at 96 h, plasma hydrocortisone concentrations returned to background with dexamethasone levels around the LOQ. Dexamethasone, formulated as phenylpropionate combined with sodium phosphate, terminal half-life, was 25.6 h in plasma and approximately 26 h in urine, and at 96 h, plasma hydrocortisone concentrations returned to background with dexamethasone levels in three of the six greyhounds around the LOQ. Critical assessment of the pharmacokinetic and pharmacodynamic data indicated how it might be utilized for medication control in racing greyhounds.

© 2019 John Wiley & Sons Ltd Medication control in greyhound racing requires information from administration studies that measure drug levels in the urine as well as plasma, with time points that extend into the terminal phase of excretion. To characterize the plasma and the urinary pharmacokinetics of flunixin and enable regulatory advice for greyhound racing in respect of both medication and residue control limits, flunixin meglumine was administered intravenously on one occasion to six different greyhounds at the label dose of 1mg/kg and the levels of flunixin were measured in plasma for up to 96hr and in urine for up to 120hr. Using the standard methodology for medication control, the irrelevant plasma concentration was determined as 1ng/ml and the irrelevant urine concentration was determined as 30ng/ml. This information can be used by regulators to determine a screening limit, detection time and a residue limit. The greyhounds with the highest average urine pH had far greater flunixin exposure compared with the greyhounds that had the lowest. This is entirely consistent with the extent of ionization predicted by the Henderson–Hasselbalch equation. This variability in the urine pharmacokinetics reduces with time, and at 72hr postadministration, in the terminal phase, the variability in urine and plasma flunixin concentrations are similar and should not affect medication control.

Animals used in sport should be treated as required to ensure animal welfare but any such use of medication should also be controlled to ensure integrity. Pharmacokinetic studies on groups of six greyhounds were performed to measure plasma and urine levels of carprofen and firocoxib to inform medication control advice. Using the standard methodology for medication control the Irrelevant Plasma Concentration was determined as 20 and 2 ng/mL for carprofen and firocoxib, respectively. The Irrelevant Urine Concentration was also determined as 0.3 and 2 ng/mL for carprofen and firocoxib, respectively. These Irrelevant Plasma and Urine Concentrations will allow laboratory Screening Limits, Detection Times and Withdrawal Time advice to be determined and publicised by regulators of greyhound racing. The Screening Limits will also inform Recommended Limits of Detection if meat-containing residues of these medications are fed to greyhounds.