Nutraceutical products containing glucosamine and chondroitin sulfate are used commonly in the performance horse business for treatment of arthritis. Regulating neutraceuticals is ultimately the responsibility of the FDA. However, there are many of these products sold with unproven label claims and advertised with illegal medical claims. Also several studies have identified the poor quality of many of these nutraceutical products. Many of the companies claim to have scientific proof that their products work when most of these studies are not actually published.
Some new information was presented at the AAEP convention regarding the effectiveness of these products. Recent clinical trials in humans have shown some benefit of these medications in mild to moderate arthritis. The positive effects on joint cartilage shown in the lab have been in studies that used very large doses compared to what is actually available in the animal. A study out of Michigan State determined that glucosamine at a dose that is actually achievable in the animal did have some effects on decreasing the chemicals that lead to arthritis in the horse. However, chondroitin sulfate showed no effect in this study although it has been shown that glucosamine and chondroitin may be more effective in combination. In the past 2 years, recent studies have shown that less than 6% of oral glucosamine is absorbed in a horse. In general, most of the positive studies of glucosamine in horses are funded by companies selling the products and independent studies are much less positive. There are lots of differences in quality of these products so check with your vet for recommendations.