Trimetoquinol: bronchodilator effects in horses with heaves following aerosolised and oral administration.
Authors: Camargo F C, Robinson N E, Berney C, Eberhart S, Baker S, Detolve P, Derksen F J, Lehner A F, Hughes C, Tobin T
Journal: Equine veterinary journal
Summary
# Editorial Summary: Trimetoquinol aerosol administration in equine heaves Whilst trimetoquinol (TMQ) has demonstrated bronchodilator properties via intravenous and intratracheal routes in horses with heaves, its efficacy and safety profile via aerosol and oral delivery remained uncharacterised. Researchers administered escalating doses of aerosolised TMQ (100–1000 µg/horse) and oral TMQ (6–60 µg/kg bodyweight) to affected horses, measuring bronchodilatory response through pleural pressure changes and monitoring cardiac effects via heart rate alongside subjective assessments of sweating, agitation and muscle trembling. Aerosolised TMQ produced robust, dose-dependent bronchodilation without alterations in heart rate or observable adverse effects, with the maximum dose (1000 µg/horse) generating a distinctive biphasic response—an immediate effect within 30 minutes followed by sustained bronchodilation between 2–4 hours post-administration—whereas the oral route proved therapeutically ineffective. These findings establish aerosol administration as a practical, well-tolerated delivery method with a favourable therapeutic index for managing airway obstruction in heaves, offering clinicians a valuable alternative to systemic bronchodilators that may carry greater cardiovascular risk in compromised respiratory cases.
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Practical Takeaways
- •Aerosolised trimetoquinol is a viable bronchodilator option for horses with heaves, with a favourable safety profile and no adverse cardiac or systemic effects at therapeutic doses
- •Expect biphasic bronchodilator response with aerosol dosing: rapid initial effect (30 min) followed by sustained effect (2-4 h), useful for planning treatment timing
- •Do not use oral trimetoquinol for heaves treatment in horses, as this route does not achieve therapeutic bronchodilator effect
Key Findings
- •Aerosolised trimetoquinol produced dose-dependent bronchodilation in horses with heaves at doses of 100-1000 microg/horse without heart rate changes or observable side effects
- •Maximum bronchodilation from aerosolised TMQ 1000 microg/horse occurred in two phases: immediate effect lasting up to 30 minutes and a second phase between 2-4 hours
- •Oral administration of trimetoquinol (6-60 microg/kg bwt) was therapeutically ineffective in producing bronchodilation
- •Aerosol administration represents a safe and effective delivery method for TMQ bronchodilation therapy in horses