A new placebo-controlled study suggests that for some low-back pain sufferers, a high dose of willow bark (Salix spp.) extract may be a safe and effective alternative to synthetic pain relievers. The willow compound salicin—first isolated from the bark in 1829—is a chemical precursor to salicylic acid, from which the active ingredient of aspirin is synthesized. Willow bark extract is commonly used today in Europe in much the same way we use aspirin to relieve pain and fever, with fewer side effects.
Only a few clinical trials have ever tested willow’s pain-relieving properties, in spite of its strong traditional reputation as an herbal analgesic. The new study showed that a 240-mg daily dose of willow bark extract was far superior to a placebo and significantly more effective than a lower willow bark dose for pain relief.
For the four-week, double-blind study, 210 people with chronic low-back pain were randomly assigned to take one of three different treatments: a high dose of willow bark extract (providing 240 mg per day of salicin), a low dose of willow bark extract (providing 120 mg per day of salicin), or a placebo. To be included in the trial, participants had to be experiencing a low-back pain flare-up that scored at least five on a standard ten-point pain-rating scale. They were permitted to supplement their test treatment with up to 400 mg a day of the prescription pain-reliever tramadol, if necessary.
The researchers judged the effectiveness of treatment by the number of people who were free of pain—without the use of tramadol—by the last week of the study. They also recorded the number of people in each study group who did require tramadol for extra pain relief. Pain relief began as early as the first week for some of the people taking the higher willow bark dose. At the end of the trial, 39 percent of people in this group were pain-free, compared with 21 percent of those taking the lower dose. Only 6 percent of people who took a placebo reported freedom from pain, and significantly more people in the placebo group chose to use tramadol during the study.
Participants reported a small number of side effects during the study, most of which were caused by tramadol. One participant had an allergic reaction (swollen eyes and itching) that the researchers believed was related to the low-dose willow bark treatment. 8
Chrubasik, S., et al. “Treatment of low back pain exacerbations with willow bark extract: A randomized double-blind study.” American Journal of Medicine 2000, 109:9–14.