Effect of salicis cortex extract on human platelet aggregation.

The bark of Salix species contains several prodrugs of salicylate, mainly salicin. The aim of this study was to investigate if during pain treatment with Salicis cortex extract platelet aggregation was affected. A total of 51 patients were enrolled in the study. Thirty-five patients suffering from acute exacerbations of chronic low back pain received randomly and double-blind either Salicis cortex extract with 240 mg salicin/day (n = 19) or placebo (n = 16). Further sixteen patients with stable chronic ischemic heart disease were given 100 mg acetylsalicylate per day. Platelet aggregation was studied using an aggregometer. As aggregating agents, arachidonic acid (500 micrograms/ml), adenosine di-phosphate (2 x 10(-5) M) and collagen (0.18 microgram/ml) were used. The mean maximal arachidonic acid induced platelet aggregation was 61%, 78% and 13% in the Salicis cortex extract, placebo and acetylsalicylate groups. Acetylsalicylate had a significant inhibitory effect on platelet aggregation compared to Salicis cortex extract (p = 0.001) and placebo (p = 0.001). There was also a significant difference between the placebo and the willow bark-treated groups in the maximal platelet aggregation induced by arachidonic acid (p = 0.04) and ADP (p = 0.01). No statistical difference was found between the groups when collagen was applied to the human platelets. Daily consumption of Salicis cortex extract with 240 mg salicin per day affects platelet aggregation to a far lesser extent than acetylsalicylate. Further investigation needs to clarify if this finding is of clinical relevance in patients with impaired thrombocyte function.