Accidental Overdose of Pergolide (Prascend) Followed by Loss of Appetite, Tachycardia, and Behavioral Abnormalities in a Pony Mare.

This research is a case study of an accidental overdose of a drug called pergolide in a 26-year-old horse. The equine suffered from tachycardia and behavioral changes but was treated successfully, providing insights into how such cases can be managed going forward.

Introduction to the Case

• A 26-year-old pony mare was presented in an emergency situation due to accidentally receiving 110 times the standard dose of pergolide, a drug used in the management of Parkinson’s disease in humans, but also used to treat pituitary pars intermedia dysfunction in horses.
• The overdose occurred approximately four hours prior to the presentation.
• The initial clinical examination revealed only a high heart rate of 52 beats per minute, termed as tachycardia.

Treatment Received

• The pony was treated first and foremost with paraffin oil and activated charcoal, delivered via a nasogastric tube. The purpose of these substances was to prevent any further systemic absorption of the pergolide, and also to speed up the intestinal excretion of the drug.
• The pony was also given azaperone, a dopamine antagonist, to counteract the effects of pergolide. The initial dose was 400mg, followed by two subsequent doses of 80mg each, and then another two doses of 60mg, all administered intramuscularly.
• In addition to this, the pony was given 40mg of verapamil, a medication commonly used to treat high blood pressure and angina, every four hours for two days and then every six hours for another five days. This was given orally.

Follow-up Observations and Recovery

• After the treatment, the horse’s condition was constantly monitored and it remained healthy in appearance and alert.
• Within a day, the pony’s heart rate had returned to normal.
• The only abnormalities noticed were a decreased in appetite and increased anxiety, especially 24 hours post ingestion, which the researchers speculate could be attributed to the dopaminergic central nervous effect of pergolide.
• However, with the passage of time, both the pony’s appetite returned and its anxiety disappeared.

Significance of the Study

• This case is significant, as overdoses of pergolide are considered very rare. To the knowledge of the authors, it is the first reported case of a severe overdose of this drug in a pony.
• The inadvertent drug overdoses are relatively common in medical practices in both human and veterinary medicine, thus, the recognition of potential side effects and knowing how to respond in such cases are critical.