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The phosphodiesterase 4 (PDE4) inhibitors constitute a relatively modern class of medications that are known for inducing bronchodilation and exhibiting anti-inflammatory properties within the body. Due to these properties, there is concern regarding their potential misuse as performance-enhancing substances in competitive sports. This study delves into the metabolic conversion of roflumilast in thoroughbred horses following oral administration and in vitro experimentation using equine liver microsomes and Cunninghamella elegans. High-performance liquid chromatography coupled with a Q Exactive Orbitrap mass spectrometer (HPLC-HRMS) was employed for analysis. The investigation identified 10 metabolites of roflumilast, including six phase I and four phase II metabolites from in vivo studies, and 11 metabolites from in vitro studies, consisting of eight phase I and three phase II metabolites. The identified biotransformation products encompassed processes such as hydroxylation, chlorine substitution, methylation, N-oxide formation, and even the dissociation of methylenecyclopropane and difluoromethane. Furthermore, the study identified three glucuronic acid and one sulfonic acid conjugated phase II metabolites of the investigated drug candidate. The aforementioned findings contribute to the detection and comprehension of the unauthorized utilization of roflumilast in equestrian sports., (© 2024 John Wiley & Sons Ltd.)

A dopamine reuptake inhibitor is a type of medication or substance that works by blocking the reuptake of dopamine in the brain. Dopamine reuptake inhibitors offer multiple effects, including increased alertness, improved mood, and therapeutic potential for conditions like depression, ADHD, and Parkinson's disease. HDMP-28, or methylnaphthidate, is a potent synthetic stimulant from the phenyltropane class. It surpasses methylphenidate in both dopamine reuptake inhibition and half-life. As a dopamine reuptake inhibitor, it boosts dopamine levels by hindering reuptake into nerve cells, resulting in heightened stimulation and increased energy. In order to comprehensively address both the tangible and potential repercussions of the unauthorized utilization of the aforementioned substance in sports, it is imperative to establish analytical methodologies for the identification of the parent drug and its primary metabolites. Additionally, a comprehensive analysis of the metabolic characteristics of HDMP-28 in both human and animal subjects has yet to be published. This study explores the metabolic conversion of HDMP-28 mediated by equine liver microsomes and Cunninghamella elegans. An extraction and detection method was developed, optimized, and validated for doping assessment in equine urine and plasma. Liquid chromatography-high-resolution mass spectrometry was employed to determine metabolite structures. The study identified 31 (22 phase I and 9 phase II) metabolites of HDMP-28, including hydroxylated, hydrogenated, and hydrolyzed analogs. Glucuronic acid-conjugated metabolites were also detected. This manuscript describes metabolites based on the in vitro studies, which might not be the same in vivo. These findings aid in the detection and understanding of the illicit use of HDMP-28 in equestrian sports., (© 2024 John Wiley & Sons Ltd.)

Nonsteroidal selective androgen receptor modulators (SARMs) are a novel class of compounds that have not yet been clinically approved; however, they appear to have a better anabolic/androgenic ratio than steroids and cause slighter side effects. Sports drug testing laboratories are required to maintain continuously updated doping control analytical methods in light of the widespread misuse of SARMs in elite and amateur sports. This paper describes the metabolic conversion of SARM GSK2881078 in thoroughbred horses following oral administration and in vitro with equine liver microsomes. A liquid chromatography-high-resolution mass spectrometry method was used to postulate the plausible structures of the detected metabolites. A total of five (M1-M5) in vivo metabolites and six (M1-M6) in vitro metabolites were detected under experimental conditions. Phase I metabolites mainly result from hydroxylation. Methoxylated and side-chain dissociated metabolites were also detected. Neither sulfonic acid nor glucuronic acid conjugated metabolites were observed in this study. Data reported here could aid in the detection of nonsteroidal SARM GSK2881078 and reveal its illicit use in competitive sports., (© 2023 John Wiley & Sons Ltd.)

Performance-enhancing substances and methods have become a serious problem in competitive sports. The hypoxia-inducible factor (HIF) stabilizers can enhance the organism's capacity for molecular oxygen transport and are likely to be abused as performance-enhancing agents in sports. This paper describes the metabolic conversion of the popular hypoxia inducible factor-prolyl hydroxylase (HIF-PH) inhibitors, namely, daprodustat, desidustat, and vadadustat using equine liver microsomes, determined on a QExactive high-resolution mass spectrometer. During this study, a total of 10 metabolites for daprodustat (all are Phase I), 10 metabolites for desidustat (five each for Phase I and Phase II), and 15 metabolites for vadadustat (six for Phase I and nine for Phase II) were detected. The important findings of the current research are as follows: (1) All the three HIF-PH inhibitor drug candidates are prone to oxidation, which results in corresponding hydroxylated metabolites; (2) in desidustat, hydrolysis and dissociation of oxime linkage also observed; (3) the glucuronic acid conjugate (except daprodustat) of the parent drugs as well as the monohydroxylated analogs were observed; (4) sulfonic acid conjugated metabolites were observed only for vadadustat., (© 2021 John Wiley & Sons, Ltd.)

ACP-105 is a novel nonsteroidal selective androgen receptor modulator (SARM) with a tissue-specific agonist effect and does not have side effects associated with the use of common androgens. This research reports a comprehensive study for the detection of ACP-105 and its metabolites in racehorses after oral administration (in vivo) and postulating its structures using mass spectrometric techniques. To obtain the metabolic profile of ACP-105, a selective and reliable LC-MS/MS method was developed. The chemical structures of the metabolites were determined based on their fragmentation pattern, accurate mass, and retention time. Under the current experimental condition, a total of 19 metabolites were detected in ACP-105 drug administered equine urine samples. The study results suggest the following: (1) ACP-105 is prone to oxidation, which gives corresponding monohydroxylated, dihydroxylated, and trihydroxylated metabolites; (2) along with oxidation, there is a possibility of elimination of water molecule (dehydration) from the third position of the tropine moiety, resulting in the dehydrated analogs of corresponding monohydroxylated, dihydroxylated, and trihydroxylated metabolites; (3) from the study on the metabolites using LC-MS/MS, it is clear that the fragmentation pattern is identical and a great number of fragment ions are common in all the metabolites and the parent drug. (4) The ACP-105 and its metabolites were detected for up to 72 h; thus, the result is a valuable tool for evaluating its use and/or misuse in sport., (© 2020 John Wiley & Sons, Ltd.)