Pergolide: Veterinarians, Horse Owners Fighting for Availability

Pergolide mesylate, a drug commonly used to treat pituitary pars intermedia dysfunction (PPID), also known as equine Cushing's disease, has been withdrawn for human use. The FDA made this announcement March 29. Since that time, horse owners and veterinarians have rallied to communicate the importance of the drug.

The issue at hand is the disappearance of the approved human drug, which veterinarians could prescribe for PPID horses, and the FDA position on compounding from bulk drugs. Because pergolide has been withdrawn for its approved use in humans, and compounding of animal drugs from bulk drug is considered illegal, there currently is no legal way for wholesalers to bring the drug into the country for compounding use.

Pergolide is considered the gold standard for treating equine Cushing's. It does not cure the disease, but it can significantly reduce the clinical signs and side effects.

"There are an estimated 10 million or so horses in the United States, about 10% of which are in an age bracket that is classically high risk for Cushing's. If only 1% of those actually need and use pergolide, that's 10,000 horses that will likely have to be put down if (they don't have) medication," said Eleanor Kellon, VMD, co-owner of the Yahoo Equine Cushing's and Insulin Resistance Group. "The actual number is likely much higher. PPID is also being diagnosed much earlier now. It wouldn't surprise me if the actual number was closer to 50,000."

If a drug is withdrawn from human use but there is a stock of the drug, that stock could be rerouted for compounding use in animals. In this case, the available stock is insufficient for the number of horses requiring treatment.

"The production of pergolide by pharmaceutical companies in the United States has stopped," Kellon said. "There is no longer any supply from this source other than what drug was already in pharmacies at the time of the FDA announcement of withdrawal on March 29. So far, none of the three companies that were producing it have any interest in manufacturing for the veterinary market."

According to Kellon, the solution to this situation requires action from FDA. The administration would need to publish a specific exception for the importation of pergolide for veterinary use, and also a specific exception to the prohibition of use of bulk drugs in veterinary compounding. There is some precedent for this, as several substances are already exempt from bulk compounding restrictions.

Kellon said she expects an official statement from the FDA to be posted on the Compliance Division section of the FDA Web site later this week. ( will alert readers when this statement is released.)

More than 2,200 horse owners, veterinarians, pharmacists, and farriers have signed an online petition to the FDA and the manufacturers of pergolide expressing the need for continued production and availability of this drug. The petition can be accessed at Kellon also suggested calling, writing, faxing, or e-mailing the FDA directly,  

"The FDA has been very responsive so far, but we don't have a solution yet and the clock is ticking for all the horses that rely on pergolide," Kellon said. "The more input we have, the easier it will be for them to see the urgency and magnitude of the problem."

For more information on the pergolide withdrawal see

About the Author

Erin Ryder

Erin Ryder is a former news editor of The Horse: Your Guide To Equine Health Care.

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