Beer AM, Wegener T. Willow bark extract (Salicis cortex) for gonarthrosis and coxarthrosis - Results of a cohort study with a control group. Phytomedicine. 2008 Nov;15(11):907-13.
In this open multicenter study, 88 patients aged 50–75 years with hip and knee osteoarthritis (OA) were treated with a standardized willow bark extract, and 40 patients received standard therapy. Most patients (92%) in the willow bark extract group were prescribed 1.572 g (equivalent to salicin 240 mg). Effectiveness of treatments was determined by clinical findings, recording of adverse events, global tolerance and by patient assessment: Western Ontario and McMaster Universities Arthritis Index (WOMAC) questions concerning pain and stiffness, and questions on general state of health. At 6 weeks from study initiation, researchers reported that the willow bark extract was superior to conventional therapy and well tolerated with no adverse effects.
Biegert C, et al. Efficacy and safety of willow bark extract in the treatment of osteoarthritis and rheumatoid arthritis: results of 2 randomized double-blind controlled trials. J Rheumatol . 2004;31:2121-2130.
This double-blind dual-RCT included the evaluation of standardized willow bark extract in patients with hip or knee OA. A total of 127 patients with WOMAC pain scores ≥30 mm were randomized to receive either willow bark extract (dosage equivalent to salicin 240 mg daily), diclofenac 100 mg daily, or placebo (n=43, 43, 41, respectively). At 6-week follow-up, differences in pain scores for those taking willow bark extract compared with placebo was not statistically significant, while the difference between diclofenac and placebo was highly significant. The investigators also conducted a pilot double-blind RCT to evaluate willow bark for rheumatoid arthritis at the same dosage, which did not show any benefit.
Schmid B, et al. Efficacy and tolerability of a standardized willow bark extract in patients with osteoarthritis: randomized placebo-controlled, double blind clinical trial. Phytother Res. 2001;15:344-350.
Willow bark extract (dosage equivalent to salicin 240 mg daily) was evaluated in this 2-week study to treat osteoarthritis. A total of 78 patients (39 extract, 39 placebo) participated in the trial. Primary outcome measured was WOMAC pain scores. Secondary outcomes included WOMAC stiffness and physical function and visual analogue scale (VAS) pain and physical function scale scores, plus final assessments by both patients and investigators. WOMAC pain score was reduced by 14% from baseline after 2 weeks of active treatment, compared with an increase of 2% in the placebo group, with significant differences between active treatment and placebo for WOMAC pain scores (d=6.5 mm, 95% CI=0.2–12.7 mm, P=.047). VAS and final overall assessments confirmed this result (patients, P=.0002; investigators, P=.0073). Investigators concluded willow bark produced a moderate analgesic effect in osteoarthritis and was well tolerated.
Chrubasik S, et al. Treatment of low back pain exacerbations with willow bark extract: a randomized double-blind study. Am J Med. 2000;109:9-14.
In this 4-week study, a total of 210 patients with exacerbated chronic low back pain were randomly assigned to receive oral willow bark extract, either low- or high-dose (120 mg or 240 mg salicin, respectively), or placebo, with tramadol as a sole rescue medication, in a 4-week blinded trial. Primary outcome measure was the proportion of patients who were pain-free without tramadol for ≥5 days during Week 4. Of 191 patients who completed the study, 27 (39%) of 65 in the high-dose group, 15 (21%) of 67 in the low-dose group, and 4 (6%) of 59 in the placebo group were pain-free during Week 4 (P<.001). Response in the high-dose group was demonstrated after only 1 week of treatment. Significantly more patients in the placebo group required tramadol (P<.001) during each week of the study. One patient in the low-dose group suffered a severe allergic reaction, possibly due to the extract.