Adverse extrapyramidal effects in four horse given fluphenazine decanoate.

The research article discusses the alarming observations in four racehorses that received the drug fluphenazine decanoate. The findings reveal that the administration of this medication can lead to severe, potentially life-threatening, neurological side effects in horses.

Details of Study and Observations

• The research centered around investigating the abnormal behaviors in four racehorses post the administration of fluphenazine decanoate, an anxiolytic not permitted for use in performance horses in many racing and horse show jurisdictions.
• The clinical symptoms exhibited by the horses included restlessness, agitation, heavy sweating, hypermetria (overstepping or high stepping), aimless circling, intense pawing, rhythmic swinging of the head and neck, alternating with severe stupor episodes.
• Presence of fluphenazine was detected in serum or plasma samples from all the four examined horses. The administered dose in three out of four horses was consistent with the range (25 to 50 mg) typically given to adult humans.

Results and Post-administration Measures

• In two horses, intravenous administration of diphenhydramine hydrochloride, an antihistamine, resulted in no positive response. Instead, these horses seemed to recover after receiving benztropine mesylate, another antihistamine primarily used to treat Parkinson’s disease, and the horses returned to racing.
• Conversely, the other two horses did respond favorably to diphenhydramine administration. While one horse resumed racing, the other horse was euthanized due to the extreme severity of neurological signs, respiratory failure, and acute kidney failure.

Conclusions

• The research concluded that the administration of fluphenazine decanoate in horses could lead to adverse extrapyramidal effects (movement disorders). The severity of these effects is unpredictable but could potentially be life-threatening.
• The research also highlighted the necessity of regulating the use of fluphenazine decanoate in performance horses, given its detectability in serum or plasma and the serious possible side effects.