Is it ethical to prescribe a placebo?

Glucosamine is a drug that is sometimes prescribed, and often recommended, to treat joint pain and arthritis. Extracted from the shells of shellfish, it isn’t toxic, and it’s relatively cheap to purchase. People who use it often notice a substantial decrease in their joint pain while they are on the medication. Unfortunately, glucosamine probably doesn’t work. Clinical evidence of its efficacy has been contradictory, at best (it’s a bit telling that the product is sold as a supplement, rather than a drug). However, in a randomized, double-blind, placebo-controlled trial, it was found to be no more effective than a placebo ¹. This would seem to indicate that any reduction in pain brought about by the drug is a result of the placebo effect, and not a medical effect.

In many ways, glucosamine is a lot like most other types of non-evidence based medical treatments. It has no proven biological effect, and any change experienced by the patient is identical to the placebo effect. However, glucosamine doesn’t exhibit most of the harms present in other quack medicine. It’s not toxic, and is relatively inexpensive; additionally, the illness that it’s meant to treat (arthritis/other joint pain) is both a) non-lethal, and b) incurable (meaning there is no harm from delaying seeking proper treatment). Treating the condition properly, one could only hope to reduce the pain — and this is already being accomplished by the placebo effect.

This creates a tough situation for the skeptically minded when we see somebody else using, or prescribing, glucosamine. On the one hand, belief in the efficacy of glucosamine is utter nonsense, and though it might not necessarily be the case, lack of skeptical thinking about one form of treatment could lead to a lack of skepticism concerning other treatments in the future. On the other hand, the harms in this case are relatively non-existent, and scientific skepticism not being too popular, skeptics are often forced to pick their battles.

What do you think?