The first scientifically controlled study in horses testing the benefit of a topical diclofenac liposomal cream on equine osteoarthritis was headed by Dr David Frisbie.

Dr Frisbie, a clinical sciences professor with expertise in joint disease, was joined by a team of researchers from the Equine Orthopaedic Research Centre at Colorado State University.

The centre is part of the university's College of Veterinary Medicine and Biomedical Sciences.

"These findings offer opportunities for a new approach to treating this debilitating disease that affects both humans and horses," said Frisbie.

"Finding a drug that treats the pain in addition to the disease allows us to provide better comfort to equine athletes with osteoarthritis while helping them improve."

The topical cream, called Surpass, contains a 1% concentration of diclofenac sodium, a common anti-inflammatory agent for people available under a number of names, including Voltaren.

Surpass cream is approved by the Food and Drug Administration for direct application to sore joints in horses.

The study tested pain relief and disease modifying potential of the product on 24 horses with a similar level of osteoarthritis at the start of the treatment period.

One-third of the horses were treated with Surpass, one-third were given oral phenylbutasone "bute", a drug known to treat osteoarthritis, and one-third were untreated.

The horses were given regular treadmill exercise five days a week for the course of the study. All horses were evaluated with regular lameness examinations, X-rays, MRIs, synovial fluid and serum tests to monitor their progress during the 10-week study.

The study showed that both Surpass and Bute decreased lameness. More significantly, the study showed that only Surpass had positive effects on the joint. MRIs of the horses in the Surpass group showed decreased bone sclerosis, decreased cartilage erosion and increased levels of a key component of cartilage. All of these results indicate an improvement in the condition.

Surpass is the first treatment in a drug classification that includes aspirin and other pain-fighting medications, to demonstrate dual action with both symptom-modifying and disease-modifying properties.

Surpass is approved in the United States as a prescription product for the control of pain and inflammation associated with osteoarthritis in horses.

The study, sponsored by IDEXX Pharmaceuticals Inc, was presented at the annual meeting of the American Association of Equine Practitioners in Orlando, Florida in December of 2007.