Both the equine practitioner and the horse owner have been barraged with a number of new treatments for arthritis in joint injury, a common problem to anyone who owns horses. Some, such as Adequan and hyaluronic acid, have been around for a while. However, more recently an intravenous formulation of hyaluronic acid has come on the market and a number of oral glycosaminoglycan products, including Synoflex, Flex-Free, Cosequin and most recently shark cartilage, are now available. All of the products may have marked beneficial effects, but in a number of instances, these have not been characterized scientifically yet.

 

 Adequan

Correctly known as polysulfated glycosaminoglycan, this product was initially licensed for intra-articular use. Controlled experiments showed that the drug used in this fashion was effective in reducing the development of osteoarthritis in chronically diseased joints. We have also found it to be a useful treatment after joint surgery when there is significant loss of articular cartilage. However, because of a slight tendency to reduce resistance to infection, antibiotics need to be given when the drug is used intra-articularly. The drug is now used most frequently in an intramuscular fashion. Effectiveness by this route has not been demonstrated as well in controlled experiments; but clinically most veterinarians recognize effects that are similar to the intra-articular route.

 

Hyaluronic Acid

This drug is a naturally occuring substance in the joint and has been used intra-articularly for nearly 20 years. There is now an intravenous preparation called Legend. Recent controlled research has shown that despite our initial skepticism, intravenous HA seems to work and there are definite benefits. Significant effects on inflammation in the joint without any compromising effects on articular cartilage have been demonstrated. Despite the short life span of hyaluronate in the blood stream, the drug has been shown to be effective in reducing inflammation over a long time period. After these results, we have started to re-evaluate our whole concept as to how some drugs used in the treament of arthritis might work. Rather than their being direct replacements for lost compounds that are important for normal joint structure or having a direct pharmacologic effect, they may stimulate various other events in a type of cascade by triggering receptors on the surface of cells.

 

Oral Glycosaminoglycans

Synoflex, Flex-Free, Cosequin shark cartilage and Cartequin are all various forms of glycosaminoglycans. Glycosaminoglycans are sugar chains that hold water and provide compressive stiffness to the articular cartilage. Adequan is also a glycosaminoglycan. They have anti-inflammatory properties and sometimes protect the articular cartilage to various degrees. We have no controlled objective work with any of these oral glycosaminoglycan products. However, many equine practitioners feel that they help the horses and they have become quite popular. Although there has not been any work done in the horse, some work in rats demonstrated that some orally ingested glycosaminoglycan can be absorbed into the bloodstream in its original form. Further work needs to be done to characterize how much makes it into the joint.

 

Corticosteroids

These are potent anti-inflammatory drugs, but the deleterious side effects have received much publicity. Recent scientific research has demonstrated that not all corticosteriods are the same and that some do not cause deleterious effects. It has recently been demonstrated that both betamethasone and triamcinolone cause no harm. In fact, triamcinolone is chondroprotective (increases the content of glycosaminoglycans in the cartilage while still exerting its anti-inflammatory effects).

In summary, the equine practitioner has quite an armament of drugs available to help the horse with joint problems. We are gradually accumulating more scientific information on these drugs to put the practitioner in a better positioner to advise the client what might be best in an individual case.

About the Author

C. Wayne Mcllwraith, BVSc, FRCVS, PhD, Dipl. ACVS, Dipl. ECVS

C. Wayne McIlwraith, BVSc, FRCVS, PhD, Dipl. ACVS, Dipl. ECVS, is Director of the Orthopaedic Research Center, Veterinary Teaching Hospital at Colorado State University, and a past president of the American Association of Equine Practitioners.

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