Phenothiazine poisoning in a thoroughbred horse.

This research paper studied a case where a 12-month-old thoroughbred horse developed acute haemolytic anaemia after being treated with a high dose of micronized phenothiazine. The horse showed improvement after receiving a range of treatments, with its haematological and biochemical levels returning to normal after 10 weeks.

Introduction and Background

• The research focuses on a distinct case of a 12-month-old thoroughbred horse. These horses are often treated with different medicines and supplements to help enhance their athletic performance and overall health.
• The horse in the study was treated with 30 grams of micronized phenothiazine, a pharmaceutical drug often used to treat psychiatric disorders in humans, such as schizophrenia and psychosis, due to its sedative and antipsychotic properties.

The Phenothiazine Poisoning

• Instead of improving the clinical status of the horse, the phenothiazine treatment triggered an acute haemolytic anaemia, a condition where red blood cells are destroyed faster than they can be produced. Key signs associated with this condition include fatigue, weakness, and shortness of breath.
• This was characterized by Heinz-body formation, small inclusions within red blood cells that are not usually present but are indicative of oxidative damage.

Other Clinical Changes and Condition Improvement

• The poisoning led to an increase in the levels of several enzymes and compounds in the horse’s blood, including serum glutamic oxaloacetic transaminase, isocitric dehydrogenase, lactate dehydrogenase, and blood urea nitrogen. These changes often indicate liver damage or disease.
• The researchers treated the horse using a range of methods to assist recovery. Treatments included blood transfusions to replace the destroyed red blood cells, fluids to ensure that the horse remains hydrated, antibiotics to ward off potential infections, and corticosteroids to reduce inflammation and support the immune system.

Outcome and Conclusion

• After systematic treatment for 10 weeks, the horse’s condition showed significant improvement. The haematological and biochemical markers returned to their normal ranges, suggesting that the tissue damage had been repaired and that the horse had recovered from the poisoning.
• This case points to the risks in administering substances like phenothiazine to animals, particularly in large doses, due to potential side effects and toxic responses. It also highlights the importance of close monitoring in medical treatments and the recovery process in horses.