Using glycosaminoglycans for treating equine joint diseases
Nov 01, 2003
During the past 20 years medical therapy for non-septic equine joint diseases and injuries has been greatly enhanced by the use of drugs classified as glycosaminoglycans (GAGs). These compounds have allowed us to direct our therapies toward the underlying pathology of equine joint disease and in many cases extend the useful careers of athletic horses. There has been an explosion in the numbers and types of these products available. Many are supported by solid scientific research and are manufactured and marketed under approval by the U.S. Food and Drug Administration (FDA). FDA approval assures that a product is safe and effective as demonstrated in controlled studies and is manufactured under strict guidelines to assure purity and potency. Others have weak or no scientific support and their manufacturing is subjected to little or no regulation. It is important that veterinarians and horse owners understand all GAG products are not equal.
What are GAGs? Glycosaminoglycans are polysaccharides made up of repeating disaccharide units and are an important component of many connective tissues including tissues in the equine joint. The most important GAGs in the equine joint are hyaluronic acid, chondroitin sulfate and keratin sulfate.
In joint inflammation and injury, these GAG components can undergo degredation due to direct injury and to the action of inflammatory mediators and catabolic enzymes. Reduced concentration and a decrease in the mean molecular weight of synovial fluid HA are early effects of synovial inflammation. The proteoglycan complexes may also be damaged or degraded and diseased cartilage is often characterized by depletion of GAG content.
The restoration of normal synovial fluid hyaluronate and repair or replacement of GAGs and other cartilage matrix components should be one of the goals of therapy for equine joint injuries.
The second approved GAG is polysulfated glycosaminoglycan or Adequan" (Luitpold). PSGAG is synthetically polysulfated chondroitin sulfate (Figure 1) which means it has a higher sulfur content compared to chondrotin sulfate. The drug is approved for intrarticular and intramuscular use in equine joint disease. The drug is anti-inflammatory, inhibits enzymes which may degrade GAGs and HA in the joint and may have a positive effect on HA and GAG synthesis in diseased joints. For this reason, PSGAG is said to be a disease modifying osteoarthritis drug. Optimal dose, efficacy and safety studies for FDA approval by the intraarticular and intramuscular route was established in six well controlled studies. Efficacy has been confirmed by at least 10 published experimental or clinical studies in the horse and nearly 20 years of clinical experience. Adequan" is indicated for the treatment of non-infectious degenerative and/or traumatic joint dysfunctions and associated lameness in the horse.