Research at the University of Sydney suggests that a new osteoarthritis drug combination could significantly extend the working life of racing and other performance horses.

Previous studies has evaluated various medications for the treatment of osteoarthritis in horses, but this is one of the first to show a new drug combination has the ability to slow down damage to joints, rather than just alleviate pain.

"Osteoarthritis is a major cause of wastage in athletic horses, with a significant economic impact on the equine industry," said Dr Toby Koenig, surgical resident at the University of Sydney Veterinary Teaching Hospital, Camden, and lead researcher for the study.

"We found a new combination of three commonly used drugs - pentosan polysulphate, glucosamine and hyaluronic acid - can reduce the damage experienced during strenuous exercise," he added.

"Until now the focus has been on minimising pain for horses suffering from osteoarthritis. We think this new drug combination could have significant impact on the way horses are treated, potentially extending careers of horses in racing, dressage and other competitive events."

The study assessed the effect, both clinical and biochemical, of a combination of pentosan polysulphate (PPS), N-acetylglucosamine (NAG) and sodium hyaluranon (HA) administered intravenously, for treating horses with experimentally induced osteoarthritis. It was carried out at the Sydney Veterinary Teaching Hospital's Research and Clinical Training Unit (REaCT) and involved horses undergoing simulated race training.

Sixteen horses with experimental lesions of the carpal (knee) joint were divided into two groups. One group received weekly intravenous injections of 3 mg/kg PPS, 4.8 mg/kg NAG and 0.12 mg/kg HA, starting ten days after the cartilage damage occurred. The second, control, group received a similar volume of saline on the same days.

Clinical, synovial fluid and biochemical changes were evaluated throughout the study. The researchers noticed no adverse effects from the treatment.

They found that the total synovial fluid protein concentration in the damaged joints was significantly lower in horses treated with PGH compared to control horses.

The results suggested that PGH had beneficial disease-modifying or chondroprotective effects and could provide a therapeutic option for osteoarthritis in horses.

Professor Andrew Dart, the Director of REaCT and one of Dr Koenig's supervisors, said the study was a significant international and multi-institutional investigation, with major implications not just for horses, but also for other species.

"The study brought together some of the world's leading researchers into equine osteoarthritis, in Australia and in the United States, to produce a significant research outcome which will impact on the welfare of horses and potentially more widely."

The research was presented at the American College of Veterinary Surgery's symposium in Chicago, in November 2011.

For more details see: Evaluation of a Combination of Pentosan Polysulphate, N-Acetylglucosamine and Sodium Hyaluronan Intravenously for Treatment of Horses with Experimentally Induced Osteoarthritis.
TJ Koenig, A Dart, N Perkins, RJ Bell, NU Horadagoda, M Krockenberger, L Jeffcott, CB Little, CW McIlwraith.
Proceedings of 2011 ACVS Symposium; Veterinary Surgery 40 (2011) E34