In clinical practice, willowbark is generally used as a symptomatic treatment in osteoarthritic conditions and lower back pain. Of the five RCTs conducted to investigate its effects in these conditions, all but one have produced positive results.
JOINT PAIN AND INFLAMMATION
Three randomised double-blind trials have investigated the efficacy of willowbark in people with osteoarthritis, with the two earlier studies finding herbal treatment produced symptom relieving effects superior to placebo. Seventy-eight subjects were randomly assigned willowbark extract (240 mg salicin/day) or placebo over a 2-week period, after which active treatment was found to produce a statistically significant improvement). Mills et al (1995), testing willowbark in 82 patients with chronic arthritic pain, also found active treatment produced a statistically significant alleviation of pain symptoms.
However, willowbark failed to reduce WOMAC pain scores better than placebo in the largest and most recent study, which involved 127 outpatients with painful hip or knee osteoarthritis. Patients were randomised to receive willow bark extract, corresponding to 240 mg of salicin/day, diclofenac 100 mg/day, or placebo. Treatment with diclofenac produced the strongest pain reducing effects (WOMAC scores decreased by 47%) compared with willowbark (17% reduction) and placebo (10% reduction), with the difference between willow bark extract and placebo not statistically significant.
Willowbark extract (corresponding to 240 mg salicin/day) failed to significantly reduce pain in people with active RA, according to a small, double-blind, randomised study of 26 volunteers. The main outcome measure used was the patient’s assessment of pain rated on a 100-mm visual analogue scale.
LOWER BACK PAIN
Two randomised studies have investigated the use of oral white willowbark in people with acute episodes of chronic non-specific low-back pain. According to a 2006 Cochrane systematic review, there is moderate evidence that a daily dose of 240 mg salicin from an extract of S. alba reduces pain more than either placebo or a daily dose of 120 mg of salicin in the short term for individuals with acute episodes of chronic non-specific low-back pain.
One randomised placebo-controlled study involving 210 patients with chronic lower back pain found that 39% of those treated with 240 mg salicin became pain free after 4 weeks compared with 6% in the placebo group. This response was achieved after 1 week. Similar results were achieved in an open trial conducted over 18 months that compared willowbark extract containing 120 mg of salicin or 240 mg salicin with what the authors term ‘conventional treatment’ in 451 people with acute exacerbations of lower back pain. Those receiving 240 mg salicin experienced the best results, with 40% pain-free after 4 weeks compared with 19% in the 120 mg salicin group and 18% in the control group.
Comparative trial with rofecoxib
No significant differences in pain relieving effects were found between white willowbark standardised to provide a daily dose of 240 mg salicin and 12.5 mg of the synthetic COX-2 inhibitor rofecoxib according to a randomised trial of individuals with acute episodes of chronic non-specific low-back pain. With regard to rescue treatments, the percentage of patients requiring NSAIDs, tramadol or both was 10% for the willowbark group and 13% for the rofecoxib group. Approximately 90% of physicians and patients rated either treatment as effective and close to 100% rated either treatment as acceptable.
Considering some pharmaceutical treatments used in the management of pain and inflammatory conditions are costly, such as the newer COX-2 inhibitors, Chrubasik et al (2001) also compared the cost savings associated with the use of willowbark. A dose of 120 mg salicin/day from willowbark reduced overall patient spending on additional drugs by about 35-50%. In comparison, 240 mg salicin/day produced superior pain relief that resulted in even less reliance on supplementary treatments, but savings were outweighed by the extra cost of the higher dose.
FEVER AND HEADACHES
Although no clinical trials are available for these indications, the known activity of the salicylate constituents suggests the herb may provide some symptomatic relief. Commission E has approved willowbark for these indications.
• Tincture (1:1): 1-2 mL three times daily.
• Decoction: 1-3 g finely chopped herb in 1 cup of cold water, brought to the boil then reduced to simmer for 5 minutes, drunk 3-4 times daily.
ACCORDING TO CLINICAL STUDIES
• Acute episodes of chronic non-specific low-back pain — willowbark preparations standardised to total salicin content and providing 240 mg daily in divided doses
None reported. Theoretically, the tannin and salicylate content may cause gastrointestinal disturbances.