Peer-reviewed veterinary case report
Adverse extrapyramidal effects in four horse given fluphenazine decanoate.
- Journal:
- Journal of the American Veterinary Medical Association
- Year:
- 2006
- Authors:
- Baird, John D et al.
- Affiliation:
- Department of Clinical Studies · Canada
- Species:
- horse
Plain-English summary
Four racehorses showed unusual and concerning behavior after receiving a medication called fluphenazine decanoate, which is sometimes used to calm animals. Their symptoms included restlessness, agitation, excessive sweating, and strange movements like circling and pawing. Blood tests confirmed the presence of fluphenazine in all four horses, and the doses given were similar to those used for humans. Two of the horses improved after receiving a different medication, while the other two had mixed results; one recovered and returned to racing, but the other had severe complications and was euthanized. This situation highlights that fluphenazine can cause serious and unpredictable side effects in horses, making its use in racing and shows risky.
Abstract
CASE DESCRIPTION: 4 racehorses were examined because of markedly abnormal behavior following administration of fluphenazine decanoate. CLINICAL FINDINGS: Clinical signs included restlessness, agitation, profuse sweating, hypermetria, aimless circling, intense pawing and striking with the thoracic limbs, and rhythmic swinging of the head and neck alternating with episodes of severe stupor. Fluphenazine was detected in serum or plasma from all 4 horses. The dose of fluphenazine decanoate administered to 3 of the 4 horses was within the range (25 to 50 mg) routinely administered to adult humans. TREATMENT AND OUTCOME: In 2 horses, there was no response to IV administration of diphenhydramine hydrochloride, but the abnormal behavior in these 2 horses appeared to resolve following administration of benztropine mesylate, and both horses returned to racing. The other 2 horses responded to diphenhydramine administration. One returned to racing. The other was euthanized because of severe neurologic signs, respiratory failure, and acute renal failure. CLINICAL RELEVANCE: Findings indicate that adverse extrapyramidal effects may occur in horses given fluphenazine decanoate. These effects appear to be unpredictable and may be severe and life threatening. Use of fluphenazine decanoate as an anxiolytic in performance horses is not permitted in many racing and horse show jurisdictions, and analytic procedures are now available to detect the presence of fluphenazine in serum or plasma.
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Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/16817724/