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Doctoral thesis, 1998

Effects of bronchodilating and non-steroidal anti-inflammatory drugs on performance potential in the horse

Kallings, Peter


This study was intended to ascertain whether or not equine performance potential is affected by non-steroidal anti-inflammatory drugs (NSAIDs; phenylbutazone, meclofenamic acid, flunixin) and bronchodilators (theophylline and clenbuterol). The latter have been illicitly adminestered to normal racehorses with the intention to ease respiration and improve oxygen uptake. In some cases use of the analgesic NSAIDs is permitted in horseracing and competitive events. However, as this use of the drugs has been questioned, it was felt important to study their effects in an objective standardized way. Clinically healthy horses therefore underwent an established submaximal exercise tolerance tests on a treadmill, both with and without medication. To study the effects of NSAIDs also during more intensive exercise, a modified standard incremental treadmill test to the point of fatigue was developed. To simulate racing conditions this test was also tried out on a track. In addition, NSAID effects on equine kinematics were studied objectively on a treadmill with high-speed cinematography in horses with low-grade lameness.

The main effects oftheophylline during submaximal exercise were increased heart rate and elevated blood lactate level, but no increase in oxygen uptake, thus suggesting impaired rather than enhanced performance potential. Clenbuterol had no major effects, thus indicating its inability to improve the performance of healthy horses.

NSAIDs also increased heart rate and caused changes in lactate responses to exercise, but as neither flunixin nor phenylbutazone altered the oxygen uptake, they too were considered not to improve performance. However, flunixin did appear to have a beneficial effect on locomotory pattern, possibly attributable to its analgesic effect on subclinical lameness or pain. In the studied lame horses, the effects of phenylbutazone remained even after its plasma concentration had fallen to a very low level.

It could then be considered that NSAIDs do not directly improve performance but, by alleviating pain, allow subclinically lame horses to run at their full potential. In racing and other competitive sports this type of therapeutic use could jeopardize the wellbeing of equine athletes.


horse; NSAIDs; bronchodilators; treadmill; track; performance; doping

Published in

Acta Universitatis Agriculturae Sueciae. Veterinaria
1998, number: 30
ISBN: 91-576-5430-1
Publisher: Swedish University of Agricultural Sciences

Authors' information

Kallings, Peter
Swedish University of Agricultural Sciences, Department of Large Animal Clinical Sciences

UKÄ Subject classification

Clinical Science

URI (permanent link to this page)