Glucosamine sulfate is a dietary supplement popularly thought to reduce the symptoms of pain, stiffness and inflammation associated with osteoarthritis. While a number of multi-year, large population, placebo-controlled studies have found statistically significant improvement in arthritis symptoms among patients receiving glucosamine sulfate after six weeks of treatment, as of 2011 few studies have shown significant levels of improvement in patients treated with the most common form of the supplement, glucosamine hydrochloride (HCl). As the United States Food and Drug Administration has not begun an evaluation of the safety or efficacy of this supplement, a review of the available scientific data on glucosamine found no significant degree of individual variability in effective dose. There are no indications that dosage adjustments to the typical adult daily dose of 1.5 g glucosamine sulfate are necessary for the accommodation of patient age, kidney health, liver function, debility or concomitant pharmaceutical regimen.
While no drug interactions with glucosamine have been established, some researchers have theorized that the supplement has the potential to interact with doxorubicin, teniposide, etoposide, warfarin, blood sugar lowering medications, insulin and non-steroidal anti-inflammatory drugs. Despite these warnings, no such interactions have been reported. Due to a reduction in the severity of pain and stiffness, some patients have reported that they have been able to reduce their use of non-steroidal anti-inflammatory medication after several weeks of a single daily 1.5 g glucosamine dose.
Some practitioners have recommended the use of a daily glucosamine dose as high as 30 g per day, given in divided doses. The use of a 30 g glucosamine dose on a regular basis, even in patients with severe arthritis, is generally considered to be excessive. Results from studies using double the standard 1.5 g daily glucosamine dose have not found a statistically significant improvement in symptom control, although higher doses increased the incidence of rare gastrointestinal side-effects like nausea and gas as well as headaches. Increases to the standard dose are not recommended.
There is no consensus in the scientific community as to the mechanism of action by which glucosamine sulfate may help reduce arthritis symptoms. Despite theoretical assertions that the supplement may help prevent damage to connective tissue, there is little evidence to support these claims. Some researchers have suggested that, while the administration of a single glucosamine dose produces little effect, cumulative doses may stimulate the synthesis of anti-inflammatory proteoglycans or may cause a reduction in the catabolic activity of chondrocyteshelping to protect articular chondrocytes and the cellular cartilage matrix. Glucosamine may also stimulate the production of hyaluronic acid, helping to decrease inflammation by enhancing lubrication in joints and inhibiting the liposomal enzymes that are responsible for cartilage degradation. As of 2011, further research is necessary to determine if and how glucosamine sulfate helps with arthritis symptoms.