In vitro and in vivo metabolism of the anabolic-androgenic steroid oxandrolone in the horse.

Oxandrolone is an anabolic-androgenic steroid with favourable anabolic to androgenic ratio, making it an effective anabolic agent with less androgenic side effects. Although its metabolism has been studied in humans, its phase I and II metabolism has not been previously reported in the horse. The purpose of this study was to investigate the in vitro metabolism of oxandrolone (using both equine liver microsomes and S9) and in vivo metabolism following oral administration (three daily doses of 50 mg of oxandrolone to a single Thoroughbred horse), using both gas and liquid chromatography-mass spectrometry techniques. The in vitro phase I transformations observed included 16-hydroxylated (two epimers), 17-methyl-hydroxylated and 16-keto metabolites. In addition to parent oxandrolone and these hydroxylated metabolites, the 17-epimer and a 17,17-dimethyl-18-norandrost-13-ene analogue were detected in biological samples following the administration. 16-keto-oxandrolone was only observed in urine. The 16- and 17-methyl-hydroxylated oxandrolone metabolites were predominantly excreted as sulfate conjugates in urine, whereas parent oxandrolone, its epimer and 17,17-dimethyl-18-norandrost-13-ene derivative were found predominantly in the unconjugated urine fraction. The most abundant analyte detected in both plasma and urine was parent oxandrolone. However, the longest detection period using the developed analytical method was provided by 17-hydroxymethyl-oxandrolone in both matrices. The results of this study provided knowledge of how best to detect the use of oxandrolone in regulatory samples.

Identification of equine in vitro metabolites of seven non-steroidal selective androgen receptor modulators for doping control purposes.

Selective androgen receptor modulators, SARMs, are a large class of compounds developed to provide therapeutic anabolic effects with minimal androgenic side effects. A wide range of these compounds are available to purchase online and thus provide the potential for abuse in sports. Knowledge of the metabolism of these compounds is essential to aid their detection in doping control samples. In vitro models allow a quick, cost-effective response where administration studies are yet to be carried out. In this study, the equine phase I metabolism of the non-steroidal SARMs GSK2881078, LGD-2226, LGD-3303, PF-06260414, ACP-105, RAD-140 and S-23 was investigated using equine liver microsomes. Liquid chromatography coupled to a QExactive Orbitrap mass spectrometer allowed identification of metabolites with high resolution and mass accuracy. Three metabolites were identified for both GSK2881078 and LGD-2226, four for LGD-3303 and RAD-140, five for PF-06260414, twelve for ACP-105 and ten for S-23. The equine metabolism of GSK-2881078, LGD-2226, LGD-3303 and PF-06260414 is reported for the first time. Although the equine metabolism of ACP-105, RAD-140 and S-23 has previously been reported, the results obtained in this study have been compared with published data.

Equine metabolism of the selective androgen receptor modulator AC-262536 in vitro and in urine, plasma and hair following oral administration.

AC-262536 is one of a number of selective androgen receptor modulators that are being developed by the pharmaceutical industry for treatment of a range of clinical conditions including androgen replacement therapy. Though not available therapeutically, selective androgen receptor modulators are widely available to purchase online as (illegal) supplement products. The growth- and bone-promoting effects, along with fewer associated negative side effects compared with anabolic-androgenic steroids, make these compounds a significant threat with regard to doping control in sport. The aim of this study was to investigate the metabolism of AC-262536 in the horse following in vitro incubation and oral administration to two Thoroughbred horses, in order to identify the most appropriate analytical targets for doping control laboratories. Urine, plasma and hair samples were collected and analysed for parent drug and metabolites. Liquid chromatography-high-resolution mass spectrometry was used for in vitro metabolite identification and in urine and plasma samples. Nine phase I metabolites were identified in vitro; four of these were subsequently detected in urine and three in plasma, alongside the parent compound in both matrices. In both urine and plasma samples, the longest detection window was observed for an epimer of the parent compound, which is suggested as the best target for detection of AC-262536 administration. AC-262536 and metabolites were found to be primarily glucuronide conjugates in both urine and plasma. Liquid chromatography-tandem mass spectrometry analysis of post-administration hair samples indicated incorporation of parent AC-262536 into the hair following oral administration. No metabolites were detected in the hair.

Analysis of supplements available to UK consumers purporting to contain selective androgen receptor modulators.

Selective androgen receptor modulators (SARMs) are compounds with specific androgenic properties investigated for the treatment of conditions such as muscle wasting diseases. The reported androgenic properties have resulted in their use by athletes, and consequently they have been on the World Anti-Doping Agency prohibited list for more than a decade. SARMs have been investigated by pharmaceutical companies as potential drug candidates, but to date no SARM has demonstrated sufficient safety and efficacy to gain clinical approval by either the European Medicines Agency or the U.S. Food and Drug Administration. Despite their lack of safety approval, SARMs are often illegally marketed as dietary supplements, available for consumers to buy online. In this study, a range of supplement products marketed as SARMs were purchased and analyzed using high resolution accurate mass - mass spectrometry to evaluate the accuracy of product claims and content labeling. This study found discrepancies ranging from a supplement in which no active ingredients were found, to supplements containing undeclared prohibited analytes. Where SARMs were detected, discrepancies were observed between the concentrations measured and those detailed on the product packaging. The outcome of this experiment highlights the high risk of such supplement products to consumers. The inaccurate product claims give rise to uncertainty over both the dose taken and the identity of any of these unapproved drugs. Even for supplements for which the product labeling is correct, the lack of complete toxicity data, especially for combinations of SARMs taken as stacks, means that the safety of these supplements is unknown.

Investigations into the analysis of intact drug conjugates in animal sport doping control - Development and assessment of a rapid and economical approach for screening greyhound urine.

Animal sport doping control laboratories are constantly reviewing ways in which they can improve their service offering whilst ensuring that they remain economically viable. This paper describes the development and assessment of a rapid and economical method for the detection of intact glucuronide conjugates of three anabolic steroids and their metabolites along with three corticosteroids in canine urine. The analysis of intact drug conjugates for animal sport doping control is generally not performed routinely as it presents a number of analytical challenges, not least of which is the lack of availability of appropriate reference standards. Here, we report the development of a UHPLC-MS/MS method using APCI in the negative ion mode for the detection of intact phase II conjugates, including the importance of in vitro incubations in order to provide appropriate reference materials. Cross-validation of the developed method demonstrated that the detection capability of the intact phase II conjugates of stanozolol, boldenone, nandrolone, and their metabolites along with the corticosteroids dexamethasone and methylprednisolone was equivalent to that achieved in routine race-day screens. The new process has been in operation for approximately 2 years and has been used to analyze in excess of 13500 canine urine samples, resulting in a number of positive screening findings. To the best of our knowledge, this is the first reported use of a routine screen for intact drug conjugates within animal sport doping control.

Re-evaluation of the pharmacokinetics of xylazine administered to Thoroughbred horses.

Xylazine is widely used worldwide as a short-acting sedative in general equine and racing practice. In the UK, although it has a legitimate use during training, equine anti-doping rules state it is a prohibited substance on race day. The aim of the study was to produce a detection time (DT) to better inform European veterinary surgeons so that xylazine can be used appropriately under regulatory rules. Previous publications have various limitations pertaining to analysis method, particularly for plasma and limited length of time of sample collection. In this study, pharmacokinetic data were produced for xylazine and 4-OH-xylazine in equine urine and plasma following a single intravenous xylazine dose of 0.4 mg/kg to six Thoroughbred horses. Pharmacokinetic parameters were generated from a 3-compartmental model with clearance = 15.8 ± 4.88 ml min-1  kg-1 , Vss = 1.44 ± 0.38 L/kg, terminal half-life = 29.8 ± 12.7 hr and a DT determined at 71 hr for the administration of xylazine (Chanazine® ) in plasma and urine. Urine screening should aim to detect the 4-OH-xylazine metabolite, which can act as an indicator for the xylazine plasma concentration. A DT of 72 hr has been agreed by the European Horserace Scientific Liaison Committee, to be implemented in June 2019.

Bioformation of boldenone and related precursors/metabolites in equine feces and urine, with relevance to doping control.

Boldenone (1-dehydrotestosterone) is an exogenous anabolic-androgenic steroid (AAS) but is also known to be endogenous in the entire male horse and potentially formed by microbes in voided urine, the gastrointestinal tract, or feed resulting in its detection in urine samples. In this study, equine fecal and urine samples were incubated in the presence of selected stable isotope labeled AAS precursors to investigate whether microbial activity could result in 1-dehydrogenation, in particular the formation of boldenone. Fecal matter was initially selected for investigation because of its high microbial activity, which could help to identify potential 1-dehydrogenated biomarkers that might also be present in low quantities in urine. Fecal incubations displayed Δ1-dehydrogenase activity, as evidenced by the use of isotope labeled precursors to show the formation of boldenone and boldione from testosterone and androstenedione, as well as the formation of Δ1-progesterone and boldione from progesterone. Unlabeled forms were also produced in unspiked fecal samples with Δ1-progesterone being identified for the first time. Subsequent incubation of urine samples with the labeled AAS precursors demonstrated that Δ1-dehydrogenase activity can also occur in this matrix. In all urine samples where labeled boldenone or boldione were detected, labeled Δ1-progesterone was also detected. Δ1-progesterone was not detected any non-incubated urine samples or following an administration of boldenone undecylenate to one mare/filly. Δ1-progesterone appears to be a candidate for further investigation as a suitable biomarker to help evaluate whether boldenone present in a urine sample may have arisen due to microbial activity rather than by its exogenous administration.

Investigation of the metabolism of the selective androgen receptor modulator LGD-4033 in equine urine, plasma and hair following oral administration.

LGD-4033 is one of a number of selective androgen receptor modulators (SARMs) that are being developed by the pharmaceutical industry to provide the therapeutic benefits of anabolic androgenic steroids, without the less desirable side effects. Though not available therapeutically, SARMs are available for purchase online as supplement products. The potential for performance enhancing effects associated with these products makes them a significant concern with regards to doping control in sports. The purpose of this study was to investigate the metabolism of LGD-4033 in the horse following oral administration, in order to identify the most appropriate analytical targets for doping control laboratories. LGD-4033 was orally administered to two Thoroughbred horses and urine, plasma and hair samples were collected and analysed for parent drug and metabolites. LC-HRMS was used for metabolite identification in urine and plasma. Eight metabolites were detected in urine, five of which were excreted only as phase II conjugates, with the longest detection time being observed for di- and tri-hydroxylated metabolites. The parent compound could only be detected in urine in the conjugated fraction. Seven metabolites were detected in plasma along with the parent compound where mono-hydroxylated metabolites provided the longest duration of detection. Preliminary investigations with hair samples using LC-MS/MS analysis indicated the presence of trace amounts of the parent compound and one of the mono-hydroxylated metabolites. In vitro incubation of LGD-4033 with equine liver microsomes was also performed for comparison, yielding 11 phase I metabolites. All of the metabolites observed in vivo were also observed in vitro.

Detection of fluticasone propionate in horse plasma and urine following inhaled administration.

Fluticasone propionate (FP) is an anti-inflammatory agent with topical and inhaled applications commonly used in the treatment of asthma in steroid-dependent individuals. The drug is used in racehorses to treat Inflammatory Airway Disease; this work was performed in order to advise on its use and detect potential misuse close to racing. Methods were developed for the extraction and analysis of FP from horse plasma and a carboxylic acid metabolite (FP-17ßCOOH) from horse urine. The methods utilize ultra high performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) in order to detect the extremely low concentrations of analyte present in both matrices. The developed methods were used to analyse plasma and urine samples collected following inhaled administration of FP to six thoroughbred horses. FP was detected in plasma for a minimum of 72 h post-administration and FP-17ßCOOH was detected in urine for approximately 18 h post-administration. The results show that it is possible to detect FP in the horse following inhaled administration.