By Mark Andrews

Long-term use of pergolide to treat horses with pituitary pars intermedia dysfunction (PPID or Equine Cushing’s disease) produces clinical improvement in most cases, and improved endocrine test results in some, according to recent work.

Pergolide has become a popular treatment for PPID in horses.  Studies have found that it is generally effective in controlling the clinical signs of PPID and that it is well-tolerated by horses when used for up to a couple of years. However, research into its long-term use has been limited.

A recent study by Harold Schott and coworkers at Michigan State University followed the outcome of longer-term treatment in PPID-affected.

Dr. Schott presented their findings at the 2022 American Association of Equine Practitioners (AAEP) Annual Convention held in San Antonio, Texas.

Approximately 20 percent of horses over age 15 will develop PPID, a progressive enlargement of the pituitary gland in the horse. The first sign of Pars Pituitary Intermedia Dysfunction (PPID) is often unexplained laminitis in the autumn. The abnormal coat of the horse with is long, curly, and non-shedding PPID. The disease cannot be cured, but if well-managed can afford many years of quality life. Photo: Shutterstock/Katarzyna Mazurowska

Thirty privately owned equids (28 horses and two ponies) being treated with pergolide for PPID were enrolled in the study. Fifteen started on a dose of one pergolide tablet (1mg) a day, and 15 started on two tablets a day. The animals were treated for periods ranging up to 12.5 years.

The research team monitored the response to treatment by contacting the owners every three months. They also examined the animals at various intervals until 12.5 years after treatment started.

Schott reported that, during the study period, five equids were euthanized for PPID-associated laminitis and 24 died or were euthanized for other age-related reasons. Survival time ranged from 0.6 to 12.5 years. The average (median) survival time was 3.3 years. One equid was still going strong at the end of the study.

Owners of 13 equids surviving after five and a half years reported continuing clinical improvement, such as healthier coat condition, better appetite, and less frequent bouts of laminitis. At that stage, 75 percent of equids had normal endocrine test results.

Seven of the 15 equids that had started on the low dose of pergolide later had the dose increased to two tablets daily. 

Schott pointed out that, although some individuals eventually needed an increased dose, that was not always the case, and some continued to have a satisfactory response to a low dose of pergolide.

Generally, owners were satisfied with the response to long-term pergolide treatment. 

For more details, see: Long-Term Response of Equids with Pituitary Pars Intermedia Dysfunction to Treatment with Pergolide; Harold C. Schott II; Julie R. Strachota; Judith V. Marteniuk; and Kent R. Refsal. Proceedings American Association of Equine Practitioners (2022) vol 68, p230.

Related: Understanding Equine Cushing's Disease

Related: Caring for the Equine Elder

Published with the kind permission of Mark Andrews, Equine Science Update