A 10-day toxicity study of toltrazuril 5% suspension in the horse.

The research explores the potential toxicity of toltrazuril, a treatment for Equine protozoal myeloencephalitis (EPM), in horses. The study findings suggest that administering toltrazuril at 50 mg/kg for 10 days triggers mild clinical abnormalities only.

Study and Procedure

• The study sought to evaluate the potential toxicity of toltrazuril when administered at a dose of 50 mg/kg for a duration of 10 days. Toltrazuril is typically used in treating Equine protozoal myeloencephalitis (EPM), a disorder that affects the nervous system of horses.
• Five horses were selected for the study, and each was given 50 mg/kg of toltrazuril once daily for the 10 days, delivered via a nasogastric tube.
• To assess the effects, complete blood cell counts, serum chemistry values, and coagulation panels were evaluated both before and after the treatment.
• On the 11th day, a full post mortem examination was performed.

Findings of the Study

• Following treatment with toltrazuril, mild clinical signs were observed. These included anorexia, weight loss, and colic, but these symptoms were only seen in one out of the five horses.
• Serum chemistry analysis revealed minimal changes, such as a mild increase in bilirubin and serum protein levels, mildly elevated hematocrit and hemoglobin concentration, and a minor increase in albumin.
• Postmortem examinations revealed Renal medullary congestion but no microscopic changes as a result of the compound administration were observed in the kidneys or any other tissues.
• The overall findings of the study suggest that the administration of toltrazuril at a dosage of 50 mg/kg for ten days led to only mild clinical abnormalities, alluding that the dosage level was tolerable. This dosage is considered to be 5 to 10 times the anticipated clinical dosage.

Conclusion

• The research indicates tolerability of toltrazuril in horses when administered at a high dosage level for a prolonged duration.
• This suggests that toltrazuril could be a potentially safe treatment for EPM, given the minimal side effects observed in the study.