A trial assessing pergolide in the treatment of Equine Cushing's disease has produced favourable results and its approval in the United States for combating the disorder is anticipated early in 2011.
 A horse with Cushing's disease. © Equine Science Update |
Results from the trial have gone to the US Food and Drug Administration (FDA) in the bid to get the drug approved.
Equine Cushing's disease - also known as pituitary pars intermedia dysfunction, or PPID - is one of the more common diseases of horses older than 15 years.
In horses with the condition, the middle lobe of the pituitary gland becomes enlarged over time and results in overproduction of hormones.
The most classic symptom is a long, curly coat that does not shed properly.
Other symptoms include excessive drinking and urination, laminitis, lethargy, excessive sweating, muscle mass loss, and repeated infections, such as sole abscesses, tooth-root infections and sinusitis.
For more than 20 years, pergolide was the drug of choice for treatment of the condition and often resulted in significant improvement to the horse's quality of life.
However, pergolide, which was an FDA-approved medication for people with Parkinson's disease, had never been officially approved for veterinary applications and had to be used "off-label".
In March 2007, the manufacturers of pergolide withdrew it from the US market after several studies revealed a link between the drug and heart valve problems after prolonged use in people with Parkinson's.
This created a wave of concern among veterinarians and horse owners about the continued availability of a drug that many had found very effective.
It continued to be available through compounding pharmacies, but FDA approval of the product for veterinary use was needed to ensure access to and the uniformity and quality of a pergolide therapy for horses.
The study included about 120 horses enrolled across the US. Michigan State University had about 40 of them, which made its veterinary teaching hospital the largest site.
Horses that were part of the trial were evaluated at the beginning of the study and then after three and six months of pergolide treatment.
Dr Hal Schott, a specialist in equine internal medicine who headed the study at the university, said: "The results proved to be quite favorable and the data have been submitted to the FDA. Approval of pergolide for treatment of PPID is anticipated in early 2011."
As part of the study, Schott, along with radiologists Tony Pease and Jennifer Kinns, also performed some CT and MRI imaging of the horses and found an enlarged pituitary, which they expected.
"We found the CT and MRI images were similar but the anatomical detail could be seen much better on MRI than CT," says Pease.
In a small number of horses that had CT imaging performed before and after treatment with pergolide, the size of the pituitary gland remained unchanged, despite marked improvement in the clinical signs of the disease.
"This was the first study to assess changes in pituitary gland size after treatment with pergolide," says Schott, "and although these imaging modalities are not necessary to diagnose [Cushings], they may prove useful in the evaluation of future additional treatment options for this disease."
Schott thanked referring veterinarians and clients who enrolled horses in the study.
"Without them, these sorts of advancement in veterinary medicine are simply not possible," he says.
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