reference
Jackson CG, Plaas AH, Sandy JD, et al. The human pharmacokinetics of oral administration of glucosamine and chondroitin sulfate individually or in combination.Osteoarthritis cartilage. 2010;18:297-302.
design
Intervention study to investigate the pharmacokinetic effects of glucosamine HCl (GHCl) and chondroitin sulfate (CS), either alone or in combination
Participant
29 healthy volunteers and 28 patients with “knee pain” that was not radiologically diagnosed as osteoarthritis
Study medications and dosage
The healthy subjects were administered single doses of GHCl (1,500 mg), CS (1,200 mg), or the combination of the two (GHCl+CS). In patients with knee pain, single doses of 1,500 mg GHCl and 1,200 mg CS were administered after 3 months of daily supplementation with GHCl (500 mg 3 times daily), CS (400 mg 3 times daily), or GHCl+CS. In both groups, pharmacokinetic measurements were performed after administration of single doses.
Primary outcome measures
Circulating glucosamine and CS levels and the area under the curve (AUC) for each.
Key findings
Somewhat surprisingly, endogenous circulating CS levels were not increased by CS supplementation, whether administered alone or with GHCl. The AUC for glucosamine was increased by supplementation with GHCl, but this increase in AUC was significantly attenuated when GHCl was combined with CS.
Effects on practice
Critics of naturopathy may have a lot to say about the findings of this new report. However, I don't believe these findings should influence how we practice. The subjects in the current study came from the Glucosamine/Chondroitin Arthritis Intervention Trial (GAIT). In contrast to most related studies, GAIT found essentially no clinical efficacy for CS or glucosamine (from GHCl). Given that the clinical results of GAIT differed from most published reports, we would not expect an examination of the pharmacokinetics of CS and GHCl used by GAIT researchers to point us to likely therapeutic mechanisms. (It remains unclear why GAIT was unable to duplicate the results of the positive randomized trials, although it is not quite the only company to report negative effects. An examination of the GAIT results shows that subjects given the combined therapies tended to have a better outcome, although none of the findings were clearly definitive.)
The current report finds that CS supplementation impairs the pharmacokinetics of GHCl and therefore may interfere with the clinical effects of GHCl. That could very well be true. In fact, the evidence to date for the use of GHCl with or without the inclusion of CS remains inconsistent and sparse. Therefore, these new findings mostly serve to further eclipse the use of GHCl, at least in combination with CS. They tell us little about the pharmacokinetics (or therapeutic effect) of the better-studied molecule glucosamine sulfate.
Although the current report does not provide a justification for choosing GHCl over glucosamine sulfate, most studies that have used GHCl report doing so because it is the most commonly available form on the market.
Although the current report does not provide a justification for choosing GHCl over glucosamine sulfate, most studies that have used GHCl report doing so because it is the most commonly available form on the market. Such justification seems questionable since most scientific evidence supports a different molecule (glucosamine sulfate).