Hi, Tracy. In brief: Prascend is only one formulation of pergolide that was effectively marketed to veterinarians as the only safe way to prescribe pergolide to horses. As Dr Kellon hinted, a big problem is that animal drugs are a tiny fraction of the pharmaceutical market, and there is no rush to market a generic to compete with Prascend.

The list of patented animal drugs is in the Green Book, and Prascend is NOT on the list.  It’s detailed, but Prascend is an FDA-approved formulation (packaging tablets in foil) shown as "effective." The manufacturer  BI *had* a period of exclusivity for that formulation that is a standard benefit of FDA approval. It is not a patent but did give the manufacturer the exclusive right to sell that formulation for 5 years. The period of exclusivity expired on September 7, 2016.

Part of BI’s business model was to convince vets that other formulations of pergolide were unstable. It’s been very effective, in part because some of those formulations really are unstable — old capsules, loose powder or pergolide suspension in water. CP in capsules, properly compounded to appropriate potency, used within 30 days, safely stored at the same temperatures as Prascend and protected from moisture, was shown in studies to be retain potency. Here's one study: https://aaep.org/sites/default/files/issues/proceedings-10proceedings-z9100110000274.pdf  

Another part of the model was to convince vets they could not prescribe compounded pergolide without risking personal liability. This was very effective initially. Broad language adopted by AAEP guidelines makes it sound like compounding is illegal and substandard, using language like, "The prescribing veterinarian should understand that his/her professional liability policy may or may not respond to allegations of negligence arising from the use of compounded drugs." As veterinarians gain more experience with CP, they find that the dire consequences of prescribing compounded pergolide are overstated.

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Cass, Sonoma Co., CA 2012
ECIR Group Moderator
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