Glucosamine for Osteoarthritis


Glucosamine, a substance derived from the shells of lobster, shrimp, and crabs - and basic to human cartilage - is an enormously popular nutritional supplement promoted for naturally treating osteoarthritis, the most common of all joint diseases. Although the long-term safety and efficacy of glucosamine have yet to be established, short-term studies, word-of-mouth, and an apparent lack of side effects have boosted demand for glucosamine as a way to relieve pain from this prevalent disorder. The Arthritis Foundation has called glucosamine and its companion, chondroitin sulfate (also a component of cartilage), "worth a try" for pain relief. Doctors report that large numbers of their patients are taking the supplement, with and without their blessing. Indeed, a Canadian article reported that more than a billion glucosamine capsules were sold in the United States in 1998.

Targeting Osteoarthritis
Osteoarthritis affects some 21 million Americans, men and women alike, but women are at particularly increased risk after menopause. Researchers suspect estrogen has a protective effect on cartilage, so the decreasing supply of it postmenopause may speed cartilage degeneration. Cartilage is the smooth, rubbery covering over the bones in the joints. Osteoarthritis develops gradually as cartilage breaks down, causing painful bone-on-bone friction. Its precise cause is unknown.

Mild and moderate osteoarthritis cases have generally been treated with nonsteroidal antiinflammatory drugs (NSAIDS) such as ibuprofen (Motrin IB, Advil) and naproxen (Naprosyn). But chronic use of these medications can cause serious gastrointestinal bleeding and ulcers. Newer, safer NSAIDS, such as the COX-2 inhibitors Celebrex and Vioxx, can cost $100 or more a month. It's little wonder so many patients are looking for gentler, less expensive ways to treat their pain.

What's Known About Glucosamine
Glucosamine occurs naturally in the body and encourages cartilage cells to produce glycosaminoglycans and proteoglycans, two protein-sugar compounds thought to stimulate the growth, repair, and maintenance of cartilage. While claims that glucosamine supplements can treat, and perhaps even slow down, osteoarthritis seem reasonable, how the body metabolizes ingested glucosamine is unclear. Researchers are unable to detect the supplement in the body once it's been taken. Commercial preparations commonly are sold as pills, liquids, and creams, and sometimes are combined with chondroitin (believed responsible for cartilage's toughness). Manufacturers generally recommend taking about 1,500 mg of glucosamine a day, although there is little science behind this dose.

Numerous European and Asian trials suggest the supplement has promise. A 1998 review of nine of these studies concluded glucosamine was apparently safe and could offer moderate short-term osteoarthritis pain relief. In two of the trials, glucosamine was compared to ibuprofen. One found the supplement to be as effective, and another found it to be more effective, than the drug. However, the average reviewed study lasted just 5.4 weeks and involved only 97 participants. Such low numbers plus sub-optimal study designs explain why most American physicians have remained skeptical. Misgivings may have begun to ease, however.

In November 1999, preliminary results of the first large clinical trial of glucosamine were presented to the American College of Rheumatology. The three-year Belgian study found the supplement not only reduced pain symptoms, but also slowed cartilage loss, a finding the researchers stress needs to be confirmed with other studies. More recently, Boston University School of Medicine researchers conducted a meta-analysis of 15 glucosamine studies published between 1966 and 1999 and concluded the supplement was effective in reducing osteoarthritis symptoms. However, they cautioned that most of the reviewed studies had some amount of sponsorship from glucosamine manufacturers.

Toward Ending the Great Debate
Because of what it terms "a real and urgent public health need" to put glucosamine (and chondroitin) to the test of a well-designed study, the National Institutes of Health (NIH) recently awarded the University of Utah School of Medicine a $6.6 million grant to coordinate the first multicenter, randomized, double-blind clinical trial of glucosamine and chondroitin in patients with osteoarthritis of the knee. More than 1,000 osteoarthritis patients will take either glucosamine, chondroitin, a combination of both, or a placebo for 16 weeks and be evaluated monthly for improvement of pain. Researchers will look at improved function as a secondary outcome.

Previous studies of glucosamine suggest it doesn't reach a level of efficacy for several weeks, and therefore should be considered a "slow-acting" drug. The Osteoarthritis Research Society suggests trials of 3-12 months for such products, clearly an unfulfilled requirement thus far. Considering the fact that osteoarthritis is a chronic disease with the potential to last for years and even decades, many experts contend the true test of glucosamine will be long-term safety and efficacy trials. In the meantime, doctors suggest taking some precautions along with glucosamine.

Taking Glucosamine
For the most part, glucosamine appears safe and has few short-term side effects. However, pregnant women, children, and very elderly people should avoid glucosamine since no studies among these specific populations exist. And patients taking blood-thinners should be extremely careful if they take glucosamine combined with chondroitin. Chondroitin is chemically similar to blood-thinning drugs such as heparin, warfarin (Coumadin), and even aspirin, and could cause excessive bleeding. Diabetics should be aware that some animal studies have shown that glucosamine increases blood sugar levels. If you haven't experienced any improvement after three months, doctors recommend you stop taking the supplement.

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