Adverse Effects of a Performance Enhancer

Researchers found that a performance-enhancing drug caused unpredictable, severe, and possibly life-threatening effects on horses. In a study completed at the University of Guelph's Ontario Veterinary College, researchers examined abnormal behavior of racehorses that were administered fluphenazine decanoate, a long-acting, antipsychotic drug used to treat humans with Schizophrenia. The study was published in the July 1 issue of the Journal of the American Veterinary Medical Association.

Researchers observed "restlessness, agitation, profuse sweating, hypermetria (an ataxic muscle disorder characterized by overreaching), aimless circling, intense pawing and striking with the thoracic limbs (forelimbs), and rhythmic swinging of the head and neck alternating with episodes of severe stupor" in four racehorses with fluphenazine decanoate in their blood.

All four horses were administered diphenhydramine hydrochloride (an antihistamine) to resolve their clinical signs caused by the performance enhancer. Two horses responded to the initial treatment; one returned to racing, and the other was euthanatized because of "severe neurologic signs, respiratory failure, and acute renal failure."

The other two horses didn't respond to the treatment, but their signs were resolved later with administration of benztropine mesylate (an anticholinergic--an agent used to block parasympathetic nerves--and antihistamine). Those two horses were able to return to racing.

Researchers noted that the side effects of fluphenazine decanoate appear to be "unpredictable and can be severe and life threatening." The drug has been banned in many racing and horse show jurisdictions, and most of these are now testing to detect its presence in serum or plasma.

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for .

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