Though it’s widely used as an alternative pain remedy, willow bark extract may not bring much relief to people with arthritis, a new study suggests.

German researchers found that six weeks of treatment with the botanical failed to ease painful symptoms among patients with either osteoarthritis or rheumatoid arthritis.

Osteoarthritis is the common form of arthritis associated with aging, while rheumatoid arthritis (RA) is an autoimmune disorder in which the immune system mistakenly attacks the lining of the joints, leading to inflammation, pain and stiffness.

Willow bark has been used for centuries as an analgesic. Its principle active ingredient is salicin, a precursor to aspirin. In Germany, preparations containing willow bark extract have been licensed by federal health officials for the treatment of arthritis.

However, the effectiveness of the alternative pain reliever has been less than clear. Two recent studies have suggested that willow bark extract may ease lower-back pain, while a two-week trial, by the same authors of the new study, found a modest benefit for osteoarthritis.

In this latest, longer study, Dr. Lutz Heide of the University of Tubingen and his colleagues followed 127 adults with osteoarthritis of the hip or knee. The patients were divided into three “arms.” Over six weeks, one group took two doses of willow bark extract every day, while another took two daily doses of the anti-inflammatory drug diclofenac, and a third took placebo pills.

In addition, the researchers followed 26 RA patients who were randomly assigned to take either willow bark extract or placebo pills for six weeks.

By the end of the study, pain scores on a standard measure had fallen among osteoarthritis patients who were on willow bark extract, but only to a degree similar to that seen in the placebo group.

In contrast, pain scores in the diclofenac group dropped significantly, by 47 percent, versus 17 percent among patients who took willow bark extract. Similarly, there was no clear benefit of the herbal product for RA patients, according to findings published in the Journal of Rheumatology.

Although earlier findings had suggested willow bark extract may aid in osteoarthritis, this study questions that notion and suggests that “a relevant efficacy in RA is very unlikely,” Heide told AMN Health.

In other research, Heide and his colleagues have found that although willow bark extract may inhibit certain inflammatory, pain-related substances in the test tube, the botanical’s active ingredients do not seem to reach high enough levels in a person’s blood to be of help.

Patients in the current study took doses of willow bark extract that corresponded to 240 milligrams of salicin a day - the dose typically recommended for pain relief.

It’s possible that higher doses would be more effective, according to Heide. He noted that reports of willow bark’s efficacy dating from the 19th century may be based on the use of very high doses.

However, Heide said, such doses would need to be studied for potential risks, and in the form of modern preparations could prove “prohibitively expensive.”

SOURCE: Journal of Rheumatology, November 2004.