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Phytomedicine. 2013 Aug 15;20(11):980-4. doi: 10.1016/j.phymed.2013.03.023. Epub 2013 Jun 2.

Willow bark extract STW 33-I in the long-term treatment of outpatients with rheumatic pain mainly osteoarthritis or back pain.

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Department of Natural Medicine, Charité University Medicine Berlin, Berlin, Germany.



Efficacy and safety of willow bark extract for pain reduction in patients suffering from musculoskeletal disorders (MSD) has been shown in clinical short term trials. Therefore this observational study over 6 months should evaluate patterns of treatments like mono- or combinations therapy, dosage and safety during long-term treatment under pragmatic conditions with the aqueous willow bark extract STW 33-I, (Proaktiv(®); drug-extract-ratio 16-23:1).


The patients were treated with STW 33-I; comedication with other NSAIDs and opioids was allowed. An extensive case report form including pain questionnaires and patient diary was used for outcome evaluation.


Four hundred and thirty-six patients with rheumatic pain mainly due to osteoarthritis (56.2%) and back pain (59.9%) were included. During the study the mean reductions from baseline value 58.4±22.6-31.8±22.5 after 24 weeks in the pain intensity scale (VAS 0-100mm) were significant even after 3 weeks with a reduction by 26 mm (45.6% of the baseline value) at the end of the study. The relative reductions of the weekly means of the daily patient self-rated scores of the pain (6-point Likert-scales) were between 33% and 44% of the baseline values during the course of the study. We present results of subgroups according their analgetic/antiphlogistic comedication. The distribution and specification of the main adverse events and the ratings of the treatment showed a good tolerability. No relevant drug interactions were reported.


These data suggest that STW 33-I can be used as a basic treatment in the long-term therapy of painful musculoskeletal disorders and that it can be combined with NSAIDs and opioids if necessary.


Back pain; Long-term-study; Osteoarthritis; Rheumatic pain; Willow bark

[Indexed for MEDLINE]

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