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

This study assessed the clinical efficacy of a chemically standardized will ow bark extract in the treatment of osteoarthritis, Willow bark extract, in a dose corresponding to 240 mg salicin/day, was compared with placebo in a 2-week, double-blind, randomized controlled trial. The primary outcome mea sure was the pain dimension of the WOMAC Osteoarthritis Index. Secondary ou tcome measures included the stiffness and physical function dimensions of t he WOMAC, daily visual analogue scales (VAS) on pain and physical function, and final overall assessments by both patients and investigators. A total of 78 patients (39 willow bark extract, 39 placebo) participated in the tri al. A statistically significant difference between the active treatment and the 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% f rom the baseline level after 2 weeks of active treatment, compared with an increase of 2% in the placebo group. The patient diary VAS confirmed this r esult, and Likewise the final overall assessments showed superiority of the willow bark extract over the placebo (patients' assessment, p = 0.0002; in vestigators' assessment, p = 0.0073). It is concluded that the willow bark extract showed a moderate analgesic effect in osteoarthritis and appeared t o be well tolerated. Copyright (C) 2001 John Wiley & Sons, Ltd.