Chromatographic detection of trimetoquinol (Inolin®) and its major urinary metabolites in the horse: A preliminary report

F. C. Camargo, A. F. Lehner, J. D. Harkins, C. G. Hughes, W. Karpiesiuk, J. Boyles, W. E. Woods, T. Tobin

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Trimetoquinol (TMQ) (1-(3′,4′,5′-trimethoxybenzyl)-6,7- dihydroxy-1,2,3,4-tetrahydroisoquinoline, m.w. 345) is the prototype tetrahydroisoquinoline pharmaceutical. TMQ is marketed as a bronchodilator in human medicine; in horse racing, TMQ is listed as an Association of Racing Commissioners International (ARCI) class 3 foreign substance. As such, TMQ is considered to have the potential to affect racing performance in horses, and a validated qualitative confirmatory method is required to regulate its use in racing. We selected 8 μg kg-1 of TMQ IV as a safe and effective dose for studies on its metabolism and analytical detection in horses. We developed a solid phase extraction method for recovery of TMQ and its metabolites from equine urine, identified suitable high performance liquid chromatographic conditions for these substances and our internal standard, papaverine, and developed a highly sensitive ESI(+)-LC-MS-MS method (estimated LOD, 100 pg mL-1) for TMQ and its major metabolites in equine urine. Multiple Reaction Monitoring (MRM) analysis of unhydrolyzed post-administration urine showed small amounts of unchanged TMQ, along with glucuronide, methylated, and sulfated metabolites, with glucuronide metabolites predominating. Following glucuronidase hydrolysis, recovered parent TMQ peaked at relatively high concentrations (>300 ng mL-1) within 1 h of administration and thereafter declined. The methylated metabolites of TMQ peaked later and at comparable total concentrations, and thereafter declined more slowly. These data suggest that glucuronide hydrolysis of post-administration urine samples will allow recovery of readily identifiable quantities of parent TMQ. These findings, combined with the highly sensitive LC-MS-MS detection of parent TMQ described herein suggest that glucuronide hydrolysis of post-administration urine, followed by LC-MS-MS or other analysis, will allow effective regulatory control of this agent in racing horses.

Original languageEnglish
Pages (from-to)371-378
Number of pages8
Issue number7-8
StatePublished - Oct 2004

Bibliographical note

Funding Information:
This work was made possible by research support from the National, Alabama, Arkansas, Kentucky, Pennsylvania, Ohio, Michigan, Charles Town WV, Florida, Nebraska, Ontario, and Canada Horsemen’s Benevolent and Protective Associations.


  • Bronchodilator in horse urine
  • Column liquid chromatography
  • Trimetoquinol

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Clinical Biochemistry
  • Organic Chemistry


Dive into the research topics of 'Chromatographic detection of trimetoquinol (Inolin®) and its major urinary metabolites in the horse: A preliminary report'. Together they form a unique fingerprint.

Cite this