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

The study focused on the pharmacodynamics of Trimetoquinol (TMQ), a bronchodilator used in human medicine, in horses affected by ‘heaves’. The research concludes that TMQ has a potent cardiac stimulant effect and offers a modest bronchodilatory function, but its associated side effects may deem it inappropriate for intravenous and intratracheal use for horses with ‘heaves’.

Research Methodology

• The team conducted an experiment involving horses affected by ‘heaves’. The objective was to assess the potential therapeutic effects of Trimetoquinol (TMQ).
• Horses were administered different doses of TMQ both intravenously (i.v.) and intratracheally (i.t.). The doses ranged from 0.001-0.2 microg/kg bwt (body weight) i.v. and 0.01-2 microg/kg bwt i.t.
• The team assessed the effects on the horses’ heart rate and airways by measuring the heart rate (HR) and the maximum change in pleural pressure (deltaPplmax), respectively.
• Subjective scoring was used to track side effects such as sweating, agitation, and muscle trembling.
• The study also explored the duration of TMQ’s action over a 6-hour period.

Results

• The experiment found that intravenous TMQ had a significant stimulant effect on the horses’ cardiac function. The heart rate initiated a rise at a dose of 0.01 microg/kg bwt, and continued to increase with the highest dose.
• Similarly, bronchodilation, as shown by a decrease in deltaPplmax, also started at a dose of 0.01 microg/kg bwt.
• When TMQ was administered intratracheally, it was 50-100 times less effective compared to its intravenous administration.
• The research noted side effects that included sweating, agitation, and muscle trembling.
• It was observed that the onset of the heart rate increase and bronchodilatory effects was rapid, beginning roughly 3 minutes after administration, but these effects surpassed by the 2-hour mark.

Conclusions

• The research concluded that TMQ, administered both intravenously and intratracheally, is a powerful cardiac stimulant but only a modest bronchodilator.
• The side effects associated with TMQ might make it an unsuitable agent for horses suffering from ‘heaves’ when administered through intravenous and intratracheal routes.
• Notwithstanding, the study suggests the need for further investigation into the administration of TMQ through oral and aerosol routes, as these may prove beneficial and safe for managing bronchoconstriction that is typical of ‘heaves’ in horses.