[Willow bark extract--effects and effectiveness. Status of current knowledge regarding pharmacology, toxicology and clinical aspects].

New pharmacological and clinical studies show that standardized willow bark extracts (WRE) is not only the natural form of salicylic acid. Willow bark extract has comparable antiinflammatory activities as higher doses of acetylsalicylic acid (ASS), and it shows antinociceptive and antipyretic activities. Under the pharmacologically active doses, no adverse effects regarding the stomach mucosa was observed, in contrast to acetylsalicylic acid. A daily dose of 1572 mg willow bark extract of a proprietary preparation (Assalix; standardised to 15.2% salicin, i.e. 240 mg salicin per day) was significantly superior to placebo in patients with osteoarthritis of the hip and the knee and in patients with exacerbations of chronic low back pain. In 2 open studies against active treatments as controls, willow bark extract exhibited advantages against a routinely prescribed treatment scheme of orthopedic specialists based on nonsteroidal antirheumatic drugs and rather similar efficacy as the COX-2-inhibitor refecoxib. Willow bark extract also displays an activity regarding the thrombocyte function, but the activity is clearly weaker.