Enantioselective disposition of (R)‐salmeterol and (S)‐salmeterol in urine following inhaled dosing and application to doping control

Abstract

Salmeterol (USAN, INN, BAN) is a long-acting beta2-adrenoceptor agonist (LABA) widely used in the treatment of airways disease. Although salmeterol is permitted via inhalation by athletes and supratherapeutic dosing may enhance performance, no urine threshold has been established by the World Anti-Doping Agency (WADA). Salmeterol is a chiral compound consisting of (R)- and (S)-enantiomers, normally administered as racemic (rac-) mixture via inhalation. Levels of rac-salmeterol in urine are often below detectable levels and there is surprisingly little information regarding the enantioselectivity of salmeterol pharmacokinetics. In this study, subjects inhaled either 50 (n = 6) or 200 µg (n = 4; generally regarded as maximum therapeutic dose) of salmeterol and urine was then collected for 24 h and analyzed by enantioselective ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Maximum rac-salmeterol urine concentrations were obtained at 2 h for both doses with medians of 0.084 ng/mL after the 50 µg dose and 2.1 ng/mL after the 200 µg dose, with an individual maximum of 5.7 ng/mL. Levels were detectable at 24 h for both doses. Salmeterol displayed enantioselective pharmacokinetics, with a mean ± SD log (S):(R) = 0.055 ± 0.025 (P < 0.0001) equivalent to (S):(R) of 1.13. In conclusion, rac-salmeterol by inhalation exhibits modest enantioselectivity in urine following single dose administration and can be detected following a single 50 µg dose for up to 24 h after inhalation. The present findings are of relevance if a urine threshold limit is to be introduced for salmeterol on the list of prohibited substances. The application of an enantiomer ratio analysis may offer improved discriminatory detection capability for doping control analysis applications. Copyright © 2016 John Wiley & Sons, Ltd.

Beta2‐adrenergic ligand racemic formoterol exhibits enantioselective disposition in blood and skeletal muscle of humans, and elicits myocellular PKA signaling at therapeutic inhaled doses

“…Enantioselective formoterol analyses follow on from our previous beta 2 ‐agonist work with the assay optimized for formoterol. Analyses were undertaken using UPLC−MS/MS consisting of a Waters Acquity ® H‐class UPLC system coupled to a Waters Xevo ® triple quadrupole mass spectrometer (Waters Corporation, Milford, MA, USA) with chromatography performed using an Astec ® CHIROBIOTIC™ T2 chiral column (4.6 × 250 mm × 5 μm particles) (Sigma‐Aldrich, St Louis, MO, USA).…”

Anabolic and lipolytic actions of beta2‐agonists in humans and antidoping challenges

“…To complicate matters, single enantiomers should be considered distinct compounds because these molecules possess different pharmacodynamics and pharmacokinetics when administered as the racemic mixture or separate enantiopure formulations . Our own work has shown distinct differences in enantiomer pharmacokinetics for beta 2 ‐agonists, including urine threshold applications . The pharmacological activity of beta 2 ‐agonists mostly resides with the (R)‐enantiomers (and (R,R)‐enantiomers), while the (S)‐enantiomers are generally considered to be pharmacological inert, such as for (S)‐salbutamol .…”

Anti-doping Policy, Therapeutic Use Exemption and Medication Use in Athletes with Asthma: A Narrative Review and Critical Appraisal of Current Regulations

“…doses administered below or within upper limits) [ 28 ]. To date, a urine threshold for salmeterol has not been implemented despite evidence concerning the ability to detect following inhalation [ 29 ]. Similarly, although differences in urinary concentrations between oral and inhaled terbutaline have been demonstrated, a threshold has yet to be established [ 30 ].…”