New Treatment for Equine Osteoarthritis Investigated (AAEP 2009)

David Frisbie, DVM, PhD, Dipl. ACVS, of Colorado State University, spoke to a large audience at the 2009 American Association of Equine Practitioners (AAEP) convention, held Dec. 5-9 in Las Vegas, Nev., about treating joint disease with a novel formulation not yet approved by the FDA.

Frisbie stressed that you have to have an accurate diagnosis to treat the problem effectively. Treatment goals for osteoarthritis are to decrease pain (using a symptom-modifying osteoarthritic drug or SMOAD) and to minimize further deterioration (using a disease-modifying osteoarthritic drug or DMOAD).

Polyglycan, the novel formulation made up of hyaluronic acid, chondroitin sulfate, and N-acetyl-D-glucosamine (HACSAG), is labeled for intra-articular post-surgical lavage and replacement of synovial fluid. It is not currently marketed or approved as a drug in the United States, although it is manufactured here in an FDA-inspected and -approved facility.

Investigators created a surgically induced cartilage fragment on a joint of each horse in three study groups. The same joint on each horse's opposite limb served as a sham control.

  • Group A: Placebo group, in which both joints were treated with saline and the antibiotic amikacin.
  • Group B: Intra-articular (IA) treatment with Polyglycan injected weekly for four treatments.
  • Group C: Intravenous (IV) treatment with Polyglycan injected every five days along with saline and antibiotic in both joints.

All horses were exercised five days per week on a high-speed treadmill beginning Day 14 and ending Day 70.

In summary, lameness in the IA-treated limbs was significantly reduced. Frisbie pointed out that this favorable result, along with reduction in gross articular changes and signs of bone growth as seen on radiographs, suggested both SMOAD and DMOAD effects. The IV-treated group showed DMOAD effects, including a significant decrease in the amount of gross pathology (disease) of full-thickness articular cartilage erosion.

Yet, investigators aren't sure why the IV-treated joints were more flexible and had fewer abnormal radiographic changes; they did not expect these results to coincide with the reported DMOAD effects. Frisbie believes it is possible that the drug's effects on soft tissues and on radiographic changes is different from its effects on articular cartilage. He noted that there are ongoing studies on IV Polyglycan therapy based on the assumption of biologic activity with this treatment approach.

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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