Glucosamine for osteoarthritis of the knee

Editor, -The article on glucosamine (Aust Prescr 2004;27:61-3) understated a couple of points. Firstly, that 'both trials were sponsored by the Rotta Research Laboratorium and used that company's formulation of glucosamine sulphate'. Surely this implies some considerable bias. Secondly, because no glucosamine product in Australia has an AUST R rating by the Therapeutic Goods Administration, does this not also imply that the products in Australia may be subject to qualitative and quantitative variations to the product studied and therefore may not produce the same or any therapeutic effect? This point is implied by the author who states 'this formulation may differ from those available in Australia'.

While glucosamine may have a unique mechanism of action, is this not thrown into doubt by the 'poor correlation between structural and symptomatic responses'? Regardless, where are the well-designed comparative trials necessary to show that glucosamine is better than standard therapy? Previous comparative trials were poorly designed, of short duration and involved small numbers.

Derek Grubb
Pharmacy Department
Bunbury Regional Hospital
Bunbury, WA

Associate Professor G. McColl, the author of the article, comments:

Both of the major randomised controlled studies were sponsored by the Rotta Research Laboratorium and this may have introduced bias into the studies. This notion, of course, would also have to apply to the majority of medications available on the Pharmaceutical Benefits Scheme, as the studies supporting their listing would also have been supported by their manufacturers.

The issue of 'qualitative and quantitative' variation in glucosamine products available in Australia is a significant one. In the purest view of evidence-based medicine we should only use the preparation that was tested in the study. As the Rotta glucosamine product is difficult to access in Australia this creates a problem. In practical terms, however, it is reasonable to extrapolate the data from these studies to 'reputable' glucosamine products in Australia, particularly if a therapeutic trial of three months is recommended.

No high quality trial has compared routine therapies such as paracetamol or non-steroidal anti-inflammatory drugs to glucosamine. I agree that this is a deficiency and will hopefully be addressed by a current study sponsored by the National Institutes of Health in the USA.