The U.S. Food and Drug Administration (FDA) will no longer support the production of compounded pergolide for use in horses, according to a recent statement from the agency. The change comes several months after the FDA approved a pergolide mesylate tablet (marketed as Prascend) for the treatment of clinical signs associated with pituitary pars intermedia dysfunction (PPID, or equine Cushing's disease).
Previously, pergolide--considered the "gold standard" for treating signs of PPID in horses--was available for use in horses via an FDA-approved formula for human Parkinson's disease. In 2007 the FDA announced that the drug was being voluntarily withdrawn from the market due to concerns about serious risk of damage to human patients' heart valves. Shortly after, the agency announced that it would permit pergolide compounding for equine use since no FDA-approved treatment options were available.
A statement issued by the FDA at that time explained that the agency would work with interested parties (i.e., veterinarians and horse owners) to ensure that a compounded pergolide product was available to treat PPID signs in horses until a new animal drug application reached approval for that use.
In 2011 the FDA approved the first pergolide mesylate product specifically designed for use in horses to treat the signs of PPID.
On March 16, 2012, the FDA released a statement indicating that "because FDA has approved (Prascend), the conditions under which the Agency was exercising enforcement discretion no longer exist" as a result of new FDA-approved product.
Philip J. Johnson, BVSc(Hons), MS, Dipl. ACVIM, Dipl. ECEIM, MRCVS, professor of internal medicine at the University of Missouri's College of Veterinary Medicine, believes that once an FDA-approved option is available, compounded medications should be avoided: "I am a strong believer that, when a private company makes effort and investment to produce and license a product--high quality, carefully packaged, stable, and produced under carefully regulated conditions--for use in horses by prescription by veterinarians, this is what we should use.
"My contention is further bolstered by the recent published work showing that several compounded products are unstable and (even) lacking the active component (pergolide)," he continued. Two examples of such studies were carried out in 2009 and 2010, respectively, and revealed that, as Johnson described, compounded pergolide has the potential to be unstable and ineffective, and vary widely in consistency from batch to batch.
"Although we have not hitherto used a lot of (the FDA-approved product) yet, it appears that a smaller quantity of Prascend is doing as much or more than larger ... doses of the compounded alternatives that have been used," Johnson said.
An FDA approval means that the product has been evaluated for safety and efficacy and that the drug has met FDA standards in regard to production to preserve its identity, strength, quality, purity, and consistency from batch to batch, and the product has demonstrated stability and effectiveness over time through a variety of environmental conditions.
Compounding pharmacies are permitted to manipulate FDA-approved products (or, in the case of pergolide from 2007 to present, from a bulk product) to produce a formulation different than what's stated on FDA-approved drug labels to meet individual animals' needs. Such formulations have not been evaluated by the FDA for safety, efficacy, stability, potency, and consistency of manufacturing.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.