Quantitative detection of salmeterol after inhalation in equine urine by liquid chromatography/tandem mass spectrometry

Doping detection in animals: A review of analytical methodologies published from 1990 to 2019

Despite the impressive innate physical abilities of horses, camels, greyhounds, or pigeons, doping agents might be administered to these animals to improve their performance. To control these illegal practices, anti-doping analytical methodologies have been developed. This review compiles the analytical methods that have been published for the detection of prohibited substances administered to animals involved in sports over 30 years. Relevant papers meeting the search criteria that discussed analytical methods aiming to detect and/or quantify doping substances in animal biological matrices published from 1990 to 2019 were considered. A total of 317 studies were included, of which 298 were related to horses, demonstrating significant advances toward the development of doping detection methods for equine sports. However, analytical methods for the detection of doping agents in sports involving other species are lacking. Due to enhanced accuracy and specificity, chromatographic analysis coupled to mass spectrometry detection is preferred over immunoassays. Regarding biological matrices, blood and urine remain the first choice, although alternative biological matrices, such as hair and feces, have been considered. With the increasing number and type of drugs used as doping agents, the analytes addressed in the published papers are diverse. It is very important to continue to detect and quantify these drugs, recognizing those that are most frequently used, in order to punish the abusers, protect animals' health, and ensure a healthier and genuine competition.

The salmeterol anomaly and the need for a urine threshold

Salmeterol is a long acting beta2-agonist (LABA) used widely for the treatment of airways disease. There is evidence that beta2-agonists, including salmeterol, have the potential for performance enhancing effects when delivered at supratherapeutic doses. For this reason, all beta2-agonists are currently on the Prohibited List issued by the World Anti-Doping Agency (WADA), regardless of dosing route with some exemptions for inhaled salbutamol, formoterol, and salmeterol when used at therapeutic inhaled doses. For 2020, salmeterol use is permitted up to a therapeutic dosing threshold of 200 μg daily, but unlike salbutamol and formoterol, there is an anomaly; currently there is no urine threshold to control for supratherapeutic dosing beyond this dosing threshold. Salmeterol, however, is reportable as an adverse analytical finding (AAF) at levels above 10 ng/mL. Complicating matters is that following inhalation, salmeterol parent drug is present at relatively low levels compared with other beta2-agonists due to rapid metabolism to the metabolite, alpha-hydroxysalmeterol, which is typically present at higher levels than the parent drug. Moreover, peak parent drug levels following permitted therapeutic dosing are below the minimum required performance level (MRPL) of 10 ng/mL for salmeterol (50% of the MRPL that analytical laboratories are required to meet for non-threshold beta2-agonists), hence the presence of salmeterol may be unreported. For consistency, a urine threshold should be introduced for salmeterol as a matter of priority, to balance the needs of athletes who use salmeterol therapeutically up to the agreed dosing threshold, with the need to control supratherapeutic dosing for doping intentions and athlete harm minimization.

Quantitative detection of inhaled salmeterol in human urine and relevance to doping control analysis

Salmeterol is a frequently prescribed β₂-agonist used for the treatment of asthma. Due to performance-enhancing effects of some β₂-agonists, salmeterol appears on the prohibited list published by the World Anti-Doping Agency and its therapeutic use is allowed but restricted to inhalation. Because the data on urinary concentrations originating from therapeutic use are limited, no discrimination can be made between use and abuse when a routine sample is found to contain salmeterol. Therefore, the urinary excretion of 100 μg of inhaled salmeterol was investigated. A liquid chromatography-tandem mass spectrometry method was developed and validated for the quantification of urine samples. Sample preparation consists of an enzymatic hydrolysis of the urine samples followed by a liquid-liquid extraction at pH 9.5 with diethyl ether/isopropanol (5/1). Analysis was performed using selected reaction monitoring after electrospray ionization. The method was linear in the range of 0.5-50 ng/mL. The limits of quantification were 500 pg/mL. The inaccuracy ranged between 10.4% and -3.7%. Results show that salmeterol could be detected for 48 hours. The maximum urinary concentration detected was 1.27 ng/mL. Cumulative data showed that only 0.27% of the administered dose is excreted as parent drug within the first 12 hours. Analysis of 47 routine doping samples, declared to contain salmeterol during routine analysis, did not exhibit concentrations that could be considered originating from supratherapeutic doses.

Minimizing matrix effects in the development of a method for the determination of salmeterol in human plasma by LC/MS/MS at low pg/mL concentration levels

Salmeterol is an inhaled bronchodilator drug used for treatment of asthma. Its concentrations in plasma are very low or undetectable by previously developed methods. The present paper describes a method for analysis of salmeterol in human plasma with 2.5 pg/mL lower limit of quantitation. Despite the basic character of the drug the method uses mixed mode anion-exchange solid phase extraction for sample preparation combined with a column switching approach to minimize matrix effects. Samples are separated and detected by LC/MS/MS. The method is easy to use, only requires 0.5 mL of plasma and was validated for use in bioanalytical applications. The method does not suffer from interference from co-administered fluticasone propionate.

Validation and application of a screening method for beta2-agonists, anti-estrogenic substances and mesocarb in human urine using liquid chromatography/tandem mass spectrometry

Electrospray ionization (ESI) mass spectra of 15 anti-estrogenic substances, beta2-agonists and mesocarb were investigated in terms of fragmentation patterns. On the basis of this product ion information, a simultaneous screening method for anti-estrogenic substances, beta2-agonists and mesocarb was developed for doping control purposes. After hydrolysis, liquid-liquid extraction was adopted for the sample preparation. The recoveries for all compounds were 30 and 96%. A single liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis could be performed in 13 min for the analysis of 15 anti-estrogenic substances, beta2-agonists and mesocarb. A quantitative analysis was also validated. Inaccuracies were below +/-12% and precisions varied from 0 to 15.8%. The limit of detection was below 10 ng/mL except formestane (300 ng/mL) and aminoglutethimide (100 ng/mL). The validated method was applied for the analysis of excretion samples.

Liquid chromatography/electrospray ionization tandem mass spectrometric screening and confirmation methods for beta2-agonists in human or equine urine

Electrospray ionization (ESI) mass spectra of 19 common beta(2)-agonists were investigated in terms of fragmentation pattern and dissociation behavior of the analytes, proving the origin of fragment ions and indicating mechanisms of charge-driven and charge-remote fragmentation. Based on these data, liquid chromatographic/ESI tandem mass spectrometric (LC/ESI-MS/MS) screening and confirmation methods were developed for doping control purposes. These procedures employ established sample preparation steps including either acidic or enzymatic hydrolysis, alkaline extraction and, in the case of equine urine specimens, acidic re-extraction of the analytes. In addition, a degradation product of formoterol caused by acidic hydrolysis during sample preparation could be identified and utilized as target compound in screening and also confirmation methods. The screening procedures cover 18 or 19beta(2)-agonists, the estimated limits of detection of which for equine and human urine samples vary between 2 and 100 ng ml(-1) and between 2 and 50 ng ml(-1), respectively. A single LC/MS/MS analysis can be performed in 9 min.