Chondroprotective agents are among the most commonly prescribed supplements in small animal practice. The most frequently used therapies include glucosamine, chondroitin and other glycosaminoglycans (GAGS), methylsulfonylmethane (MSM) and cetyl myristoleate (CM).
What Are They?
Glucosamine is an aminosugar made from glutamine and glucose that is produced naturally in the body and is used for synthesis of cartilage. It is supplied in one of three forms: Glucosamine sulfate, glucosamine hydrochloride (a salt of D-glucosamine; D-glucosamine is eventually converted by the body into glucosamine sulfate), or N-acetylglucosamine. Glucosamine is not usually obtained directly from food; supplements are derived from chitin, a substance found in the shells of shrimp, lobsters and crabs.
Studies show that while all three forms of glucosamine are effective, glucosamine hydrochloride (which is a salt of D-glucosamine) and glucosamine sulfate were more effective than N-acetylglucosamine.1 Results take four to eight weeks to develop. These improvements often last for several weeks after glucosamine supplements are discontinued.
Glycosaminoglycans (GAGS) are aminosugars that are part of the proteoglycan structure that cross-link with collagen in cartilage. Chondroitin sulfate is the major glycosaminoglycan found in cartilage. Animal cartilage (bovine, shark) is the most common dietary source of chondroitin. Another supplement, perna mussels, contains small amounts of chondroitin and other GAGS as well. Because chondroitin production by the body decreases with aging, supplementation with this compound may be especially helpful for older pets with arthritis. One novel product called Adequan contains glycosaminoglycans extracted from bovine cartilage and is available in an injectable form.
Methylsulfonylmethane (MSM) is a natural anti-inflammatory and analgesic that is a stable metabolite of DMSO (dimethylsulfoxide). MSM is found naturally in a variety of foods including meat, fish, eggs, poultry, milk, and in leser amounts in vegetables, legumes and fruits. The amount of MSM in the body decreases with age, indicating a possible need for this compound in our older pets.
Cetyl myristoleate (CM) is a fatty acid ester of a fatty acid (myristoleic acid) commonly found in fish oils, butter and animal fat.
How Do They Work?
The various supplements are believed, in general, to reduce inflammation and pain and assist in cartilage healing. Glucosamine is rapidly taken up by cartilage cells and helps stimulate the synthesis of synovial fluid and cartilage and also helps inhibit the destructive enzymes that can destroy cartilage and proteoglycans.2 The anti-inflammatory aspect of glucosamine may result from the scavenging of harmful free radicals (similar to antioxidants).
Chondroitin is theorized to work by providing cartilage with the molecules it needs to repair itself. It is also believed to block enzymes that break down cartilage in the joints. Another theory holds that chondroitin increases the amount of hyaluronic acid in the joints. Finally, chondroitin may have a mild anti-inflammatory effect.
In general, GAGS exhibit anti-inflammatory properties and act in the repair process of damaged cartilage.3
MSM supplies sulfur to the body, which is an essential chemical needed for the synthesis of cartilage. In arthritic cartilage, the concentration of sulfur is about one-third the level found in normal cartilage. MSM is proposed to help treat arthritis by providing sulfur used by the cartilage in the healing process.4
The exact mechanism of action of cetyl myristoleate (CM) is unknown, but it is presumed to act similarly to omega-3 fatty acids (its effects, however, are often seen more quickly and last longer than when fatty acid supplements are used by themselves). It has been proposed that CM may function as a joint lubricant, an anti-inflammatory and a repolarizer of cells.5
Evidence of Effectiveness
A number of studies in people and pets show the effectiveness of chondroprotective nutraceuticals.6 to 13
The studies indicate that these products are equally effective (if not more effective) when treating osteoarthritis as traditional NSAID (Nonsteroidal anti-inflammatory drug) therapy without the associated side effects. While NSAID therapy works more quickly (there is often a lag time of four to eight weeks before effectiveness is seen when using chondroprotective nutraceuticals), nutraceuticals have a residual effect that occurs even after the product is no longer given. This residual effect is not reported with NSAID therapy and is another benefit of using chondroprotective nutraceuticals.
What Is the Dosage?
The recommended daily starting dose of glucosamine is 1,000 to 1,500 mg for a 50 to 100 pound dog. The recommend daily starting dose of chondroitin is 800 to 1200 mg for a 50 to 100 pound dog.
A recommended starting dose for cats and small dogs (under 30 pounds) for MSM is 100 to 200 mg twice daily, mixed in with food (the bitter taste is unpleasant). Larger patients can receive double the dose.
A recommended dosage for CM is 385 mg twice daily for small dogs and cats, 770 mg twice daily for medium dogs and 1155 mg twice daily for large dogs given with digestive enzymes for maximum absorption.
The recommended dosage for the injectable form of GAGS (Cosequin) is 4.4 mg/kg IM weekly.
Are Their Any Safety Issues or Precautions?
These compounds are very safe when used as prescribed. Because glucosamine is an aminosugar, there is some concern that glucosamine may elevate blood glucose levels, although this has not been proven to be a problem in dogs and cats. As a result, diabetic patients should have blood glucose levels monitored during therapy with glucosamine.14
Chondroitin sulfate, like glucosamine, has not been associated with any serious side effects.
MSM is considered very safe; the lethal dose of MSM in mice starts at 20 grams/kg of body weight. No long-term side effects were seen when human volunteers were given MSM for up to six months. CM is also considered safe when used as directed.
Side effects with injectable GAGS are extremely rare but are reported to include a dose-dependent inhibition of blood clotting.
The decision to use a chondroprotective supplement is easy as many are proven effective for minimizing joint pain and inflammation and assisting in cartilage healing. There are many types of supplements and it may not be easy to determine which supplement to recommend. While most supplements will help all but the most severely arthritic pet, trial and error will determine which supplement is most effective in any individual patient.
Shawn Messonnier, D.V.M., is a holistic veterinarian and nationally recognized expert on integrative medicine for animals. He is the author of several books, including the award-winning Natural Health Bible for Dogs and Cats, The Allergy Solution for Dogs and The Arthritis Solution for Dogs.
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