Salmeterol is a drug used for the treatment of airway diseases such as asthma. It is a chiral compound and most often administered in a 50:50 racemic mixture via inhalation. Only the (R)-salmeterol enantiomer causes a pharmacological response, while the (S)-enantiomer is considered pharmacologically inert.

For athletes, there is a permitted maximum of salmeterol of 200 µg in 24 h because the compound enhances exercise performance. Unfortunately, there is no urine threshold, as the enantioselective urinary pharmacokinetics are unknown, making effective doping controls impossible.

Glenn Jacobson, University of Tasmania, Australia, and colleagues used ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for the enantioselective salmeterol analysis of urine samples following a single administration of therapeutic doses of salmeterol (50 µg and 200 µg, respectively).

The team found that salmeterol can be detected for up to 24 hours after inhalation following a single 50 µg dose. The results also show that salmeterol displays some enantioselectivity in urinary pharmacokinetics. According to the researchers, these findings are relevant for the introduction of a urine threshold limit for salmeterol on the list of prohibited substances.

• Enantioselective disposition of (R)-salmeterol and (S)-salmeterol in urine following inhaled dosing and application to doping control,
  Glenn A. Jacobson, Morten Hostrup, Christian K. Narkowicz, David S. Nichols, E. Haydn Walters,
  Drug Test. Anal. 2016.
  DOI: 10.1002/dta.2131