Liquid chromatography-tandem mass spectrometry and confirmation by liquid chromatography-high-resolution mass spectrometry hair tests to evidence use of tizanidine by racing cyclists.

Tizanidine, an imidazoline derivative close to clonidine, is a central alpha-2 adrenergic receptor agonist. Therapeutically, the drug is used as a muscle relaxant under the trade names Sirdalud™ or Zanaflex™. The drug is not prohibited by the World Anti-Doping Agency but, for therapeutic purposes, can only be obtained via a nominative temporary use authorization. The French public health police requested the laboratory to test for tizanidine in head hair specimens collected from international racing cyclists. Using Liquid chromatography-tandem mass spectrometry (LC/MS-MS) and confirmation by liquid chromatography-high-resolution mass spectrometry (LC/HRMS), after pH 9.5 borate buffer overnight incubation of 20 mg and subsequent solvents extraction, tizanidine was identified in the hair of three athletes at 1.1, 3.7, and 11.1 pg/mg. This is the first evidence that tizanidine is incorporated in human hair. However, it was not possible to interpret the data in terms of doses and frequency of use due to a lack of controlled study.