Intravenous and intratracheal administration of trimetoquinol, a fast-acting short-lived bronchodilator in horses with 'heaves'

F. C. Camargo, N. E. Robinson, C. Berney, S. Eberhart, S. Baker, P. DeTolve, F. J. Derksen, J. D. Harkins, A. F. Lehner, T. Tobin

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Reason for performing study: Trimetoquinol (TMQ) is a potent β-adrenoceptor agonist bronchodilator used in human medicine but has not been evaluated for potential use as a therapeutic agent for horses with 'heaves'. Objectives: To assess the pharmacodynamics of TMQ in horses with 'heaves' to determine potential therapeutic effects. Methods: Increasing doses of TMQ were administered to horses with 'heaves' by i.v. and intratracheal (i.t.) routes. Doses ranged 0.001-0.2 μg/kg bwt i.v. and 0.01-2 μg/kg bwt i.t. Cardiac and airways effects were assessed by measurement of heart rate (HR) and maximal change in pleural pressure (ΔPplmax), respectively. Side effects of sweating, agitation and muscle trembling were scored subjectively. Duration of action to i.v. (0.2 μg/kg bwt) and i.t. (2 μg/kg bwt) TMQ was evaluated over 6 h. Results: Intravenous TMQ was an exceptionally potent cardiac stimulant. Heart rate increased at 0.01 μg/kg bwt, and was still increasing after administration of highest dose, 0.2 μg/kg bwt. Airway bronchodilation, measured as a decrease in ΔPplmax, also commenced at 0.01 μg/kg bwt. By the i.t. route, TMQ was 50-100-fold less potent than by i.v. Side effects included sweating, agitation and muscle trembling. Overall, the onset of HR and bronchodilator effects was rapid, within about 3 min, but effects were over at 2 h. Conclusion: When administered i.v. and i.t., TMQ is a highly potent cardiac stimulant and a modest bronchodilator. It may not be an appropriate pharmacological agent by i.v. and i.t. routes for the alleviation of signs in horses with 'heaves'. Further studies of TMQ by oral and aerosol routes are necessary. Potential relevance: In horses, TMQ is a fast-acting bronchodilator with a short duration of action. It could be used as a rescue agent during an episode of 'heaves'. The i.v. and i.t. administration of TMQ is associated with side effects, similar to those reported for all other β-agonists. However, other routes, such as aerosol and oral, may prove useful and safe for the alleviation of bronchoconstriction typical of 'heaves'.

Original languageEnglish
Pages (from-to)563-569
Number of pages7
JournalEquine Veterinary Journal
Issue number6
StatePublished - 2006


  • Beta-adrenergic agonist
  • Heart rate
  • Horse
  • Pleural pressure
  • Sweating
  • TMQ

ASJC Scopus subject areas

  • Equine


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