Efficacy and tolerability of a standardized willow bark extract in patients with osteoarthritis: randomized, placebo-controlled, double blind clinical trial

Objective: To assess the clinical efficacy of a chemically standardized wil low bark extract in the treatment of osteoarthritis. Methods: Willow bark e xtract, in a dose corresponding to 240 mg salicin/day, was compared to plac ebo in a 2-week, double-blind, randomized controlled trial. The primary out come measure was the pain dimension of the WOMAC Osteoarthritis Index. Seco ndary outcome measures included the stiffness and physical function dimensi ons of the WOMAC, daily visual analogue scales (VAS) on pain and physical f unction, and final overall assessment by both patients and investigators. R esults: 78 patients (39 willow bark extract, 39 placebo) participated in th e trial. A statistically significant difference between active treatment an d placebo group was observed in the WOMAC pain dimension (d=6.5 mm, 95% C.I .=0.2-12.7 mm, p=0.047); the WOMAC pain score was reduced by 14% from basel ine level after two weeks of active treatment, compared to an increase of 2 % in the placebo group. Patient diary VAS confirmed this result, and likewi se the final overall assessments showed superiority of willow bark extract over placebo (patients assessment, p=0.0002; investigators assessment, p=0. 0073). Conclusion: Willow bark extract shows a moderate analgesic effect in osteoarthritis.