Trimetoquinol Hydrochloride Hydrate

Tretoquinol (trimetoquinol), a β2‐agonist, has been explicitly listed on the World Anti‐Doping Agency Prohibited List 2019 since January 2019; however, it has been distributed as an antiasthmatic on the medical market. This study aimed to develop a liquid chromatography–tandem mass spectrometric method for the quantification of tretoquinol (free form plus glucuronide) in human urine for doping control purposes. An excretion study (n = 6) of tretoquinol hydrochloride hydrate (6 mg) was performed, and urine samples were collected prior to oral administration and during the first 48 h, along with spot urine samples at 7 and 14 days after administration. All the urine samples were analysed using the developed method. The limit of detection for the developed method was 0.03 ng/mL. The inter‐day precision for the target analyte was excellent (2.7% to 9.2%), and the inter‐day accuracy of target analyte was −0.6% to −3.6%. In all subjects, tretoquinol (free form plus glucuronide conjugate) was identified up to 48 h after administration. The maximum concentrations were in the range of 12.4–78.8 ng/mL and the mean concentration was 55.3 ng/mL. The metabolites O‐methylated tretoquinol, tretoquinol sulphate and O‐methylated tretoquinol sulphate could be also identified in human urine after administration. The longest‐lasting urinary metabolite of tretoquinol currently known, O‐methylated tretoquinol, is also likely to be a useful marker in doping controls.