Pergolide Withdrawal Draws Fire from Horse Owners

On March 29, 2007, the FDA announced the voluntary withdrawal of pergolide from the human market. Pergolide is used to treat Parkinson’s disease and some other conditions in humans, but recent studies have shown up to 22% of human users may develop detectable abnormalities in their heart valves.

Pergolide is not an approved veterinary drug, but it has been the drug of choice for managing Cushing’s disease/PPID (pars pituitary intermedia dysfunction) in horses for 10 to 15 years. There have been no recognized instances of cardiac valvular problems in horses on pergolide, even after many years of continuous use. This may be related to the fact that horses with PPID respond to dosages that are much lower — only the equivalent of a low/moderate dose for a human — so their dose per body size is much smaller. Most horses on pergolide are on compounded preparations of the drug or the generic pills.

Horses on pills, or compounded pergolide made from pills, are already running out of medication. Although compounders could get supplies from outside the United States, the FDA has clearly stated that compounding from bulk drugs is illegal. With the withdrawal of pergolide from human use and no other FDA-approved use for the drug, it is also subject to seizure by U.S. Customs.

Some people have been told by their compounding pharmacies that the withdrawal for human use doesn’t involve pergolide for horses. That’s true, but it’s also not the problem. The problem is supply. If those compounders are relying on FDA-approved drug wholesalers to supply them, they’re in for a rude awakening. Some compounders claim to have large amounts in stock, but many are running out. As more veterinarians turn to the better-stocked pharmacies, they, too, will come up short.

The owner of one of the largest veterinary compounding pharmacies in the country told us they provide pergolide for around 5,000 individual horses and hundreds of vet clinics. That’s just one pharmacy. He estimates that by the time you read this, the U.S. supply will be exhausted, and it takes a month after placing an order for it to arrive in the country and clear U.S. Customs.

The withdrawal of pergolide isn’t likely to have much impact on human patients, who have established alternatives. Horses are a different story. Vitex agnus-castus, first reported in a December 2000 Horse Journal trial to be effective symptomatically, doesn’t always improve laboratory markers of the disease and may lose effectiveness over time. The same is true for a previous drug used, cyproheptadine.

Pergolide is by far the most reliable, effective Cushing’s disease treatment. Although other drugs have similar effects, we have no information on correct dosages, safety or long-term effectiveness like we do for pergolide.

Getting The Drug Back

When news of the withdrawal was made public, members of the Equine Cushing’s and Insulin Resistance group researched the implication, established contact with drug wholesalers and the defunct pill manufacturers to educate them as to the ongoing need, established a dialog with the FDA and set up an online petition,

Subsequent efforts focused on educating the individual state pharmacy boards and veterinary associations, the American Veterinary Medical Association and the American Association of Equine Practitioners.

On April 18, the AAEP issued a statement in support of urging the FDA to grant an exception to the prohibition on compounding from bulk drugs, so that horses can continue to receive the drug they need.

Efforts to motivate the FDA to put in place at least an interim solution are ongoing, but will likely bog down until a crisis is reached or until the sheer volume of public outcry forces it.

No horse should have to go without treatment and be put at risk of developing laminitis or other life-threatening complications of Cushing’s because the FDA and compounders are feuding.

Bottom Line

We believe it’s the FDA’s responsibility to keep the supply of pergolide uninterrupted to the horses that need it. There’s no reason why even one horse should have to suffer. The FDA can publish an exemption to the prohibition of compounding from bulk drugs with specific reference to pergolide for horses. Urge them to do it before the impending disappearance becomes a reality.

What did you think of this article?

Thank you for your feedback!