Health Care Professional Information

Scientific Name
Salix alba
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Common Name

Bay willow, black willow, white willow

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Clinical Summary

Willow bark has been used for thousands of years in China and Europe as a remedy for fevers, pain and inflammation. It contains salicin, the phytotherapeutic precursor of aspirin (acetylsalicylic acid).
Willow bark extracts exert anti-inflammatory (1), antiplatelet (2) and antiproliferative (3) effects in vitro. Clinical studies demonstrate their efficacy in the management of back pain (4), osteoarthritis (5), gonarthrosis and coxarthrosis (6). A systematic review suggests it may also be effective in treating low back pain (7).
Topical application of salicin may help reduce aging of the skin (9).

Conclusions of a meta analysis support use of aspirin as a preventative in patients at increased risk of occlusive vascular events, including those with an acute myocardial infarction or ischemic stroke, angina, previous myocardial infarction, stroke, peripheral arterial disease or atrial fibrillation (8).
In 1985, the United States Food and Drug Administration approved aspirin for the treatment and secondary prevention of acute myocardial infarction.

Recent data from epidemiologic and observational studies suggest that aspirin has clinically relevant anticancer effects (10) (11). However, it is not known if willow bark has the same effects.

Because willow bark supplements can have additive effects with non steroidal anti-inflammatory drugs, they should not be given concurrently. Children should not be given willow bark because of the potential for developing Reye syndrome, a serious condition associated with the use of aspirin.

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Purported Uses
  • Fever
  • Headaches
  • Inflammation
  • Influenza
  • Muscle pain
  • Pain
  • Weight loss
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Constituents
  • Salicin and Salicin derivatives
  • Catechol
  • Flavonoids
  • Phenols
  • Tannins
  • Ampelopsin, taxifolin, 7-O-methyltaxifolin-3'-O-glucoside, 7-O-methyltaxifolin and ethyl 1-hydroxy-6-oxocyclohex-2-enecarboxylate
    (12) (13) (19)
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Mechanism of Action

Willow bark extracts demonstrate anti-inflammatory effects that were shown to be due to inhibition of pro-inflammatory cytokines (tumor necrosis factor-alpha), cyclo-oxygenase (COX-2) and nuclear translocation of the transcription factor NF-κB (1). The active compound has been identified as salicin (19). But another study showed involvement of catechol as well in the anti-inflammatory activity along with salicin and flavonoids (13).
Willow bark extract was also found to raise the levels of GSH (reduced glutathione) significantly, an effect that helps to limit lipid peroxidation (14).
The antiproliferative effects of willow bark extracts on human colon and lung cancer cells are due to their growth-inhibitory and apoptosis-inducing properties (15).
Aspirin was shown to overcome tumor resistance and enhance the effectiveness of interferon-alpha against hepatocellular carcinoma by activating the STAT1 gene (16).

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Adverse Reactions

Willow bark supplements can cause anaphylactic reactions (17) and can affect platelet aggregation (2).

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Herb-Drug Interactions

Warfarin: When used concurrently, willow bark may increase the risk of bleeding (18).

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Literature Summary and Critique

Beer AM, Wegener T. Willow bark extract (Salicis cortex) for gonarthrosis and coxarthrosis - Results of a cohort study with a control group. Phytomedicine. 2008 Nov;15(11):907-13.
In this open, multi-centric study, 88 patients, ages between 50 and 75, with gonarthrosis and coxarthrosis were treated with a standardized willow bark extract, and 40 patients with standard therapy. Effectiveness of the treatments was determined by clinical findings, recording of adverse events, global tolerance and by patient assessment (WOMAC questions concerning pain and stiffness, questions on general state of health). At 6 weeks from the initiation of the study, researchers reported that the willow bark extract was superior to conventional therapy. It was well tolerated with no adverse effects.

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Dosage (Inside MSKCC Only)
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References
  1. Bonaterra GA, Heinrich EU, Kelber O, et al. Anti-inflammatory effects of the willow bark extract STW 33-I (Proaktiv(®)) in LPS-activated human monocytes and differentiated macrophages. Phytomedicine. 2010 Dec 1;17(14):1106-13.
  2. Krivoy N, Pavlotzky E, Chrubasik S, et al. Effect of salicis cortex extract on human platelet aggregation. Planta Med. 2001 Apr;67(3):209-12.
  3. Bonaterra GA, Kelber O, Weiser D, Metz J, Kinscherf R. In vitro anti-proliferative effects of the willow bark extract STW 33-I. Arzneimittelforschung. 2010;60(6):330-5.
  4. Chrubasik S, Eisenberg E, Balan E, et al. Treatment of low back pain exacerbations with willow bark extract: a randomized double-blind study. Am J Med 2000;109:9-14.
  5. Schmid B, Lüdtke R, Selbmann HK, et al. Efficacy and tolerability of a standardized willow bark extract in patients with osteoarthritis: randomized, placebo-controlled, double blind clinical trial. Phytother Res 2001;15:344-50.
  6. Beer AM, Wegener T. Willow bark extract (Salicis cortex) for gonarthrosis and coxarthrosis - Results of a cohort study with a control group. Phytomedicine. 2008 Nov;15(11):907-13.
  7. Vlachojannis JE, Cameron M, Chrubasik S. A systematic review on the effectiveness of willow bark for musculoskeletal pain. Phytother Res. 2009 Jul;23(7):897-900. Review.
  8. Antithrombotic Trialists' Collaboration. Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients. BMJ. 2002;324:71– 86.
  9. Gopaul R, Knaggs HE, Lephart JF, et al. An evaluation of the effect of a topical product containing salicin on the visible signs of human skin aging. J Cosmet Dermatol. 2010 Sep;9(3):196-201.
  10. McCowan C, Munro AJ, Donnan PT, Steele RJ. Use of aspirin post-diagnosis in a cohort of patients with colorectal cancer and its association with all-cause and colorectal cancer specific mortality. Eur J Cancer. 2013 Mar;49(5):1049-57.
  11. Gamba CA, Swetter SM, Stefanick ML, et al. Aspirin is associated with lower melanoma risk among postmenopausal Caucasian women: the Women's Health Initiative. Cancer. 2013 Apr 15;119(8):1562-9.
  12. Agnolet S, Wiese S, Verpoorte R, Staerk D. Comprehensive analysis of commercial willow bark extracts by new technology platform: combined use of metabolomics, high-performance liquid chromatography-solid-phase extraction-nuclear magnetic resonance spectroscopy and high-resolution radical scavenging assay. J Chromatogr A. 2012 Nov 2;1262:130-7.
  13. Freischmidt A, Jürgenliemk G, Kraus B, et al. Contribution of flavonoids and catechol to the reduction of ICAM-1 expression in endothelial cells by a standardised Willow bark extract. Phytomedicine. 2012 Feb 15;19(3-4):245-52.
  14. Khayyal MT, El-Ghazaly MA, Abdallah DM, et al. Mechanisms involved in the anti-inflammatory effect of a standardized willow bark extract. Arzneimittelforschung 2005;55(11):677-87.
  15. Hostanska K, Jürgenliemk G, Abel G, Nahrstedt A, Saller R. Willow bark extract (BNO1455) and its fractions suppress growth and induce apoptosis in human colon and lung cancer cells. Cancer Detect Prev. 2007;31(2):129-39.
  16. Li T, Dong ZR, Guo ZY, et al. Aspirin enhances IFN-α-induced growth inhibition and apoptosis of hepatocellular carcinoma via JAK1/STAT1 pathway. Cancer Gene Ther. 2013 May 24. [Epub ahead of print]
  17. Boullata JI, McDonnell PJ, Oliva CD. Anaphylactic reaction to a dietary supplement containing willow bark. Ann Pharmacother. 2003 Jun;37(6):832-5.
  18. Shalansky S, Lynd L, Richardson K, et al. Risk of warfarin-related bleeding events and supratherapeutic international normalized ratios associated with complementary and alternative medicine: a longitudinal analysis. Pharmacotherapy. 2007 Sep;27(9):1237-47.
  19. Fuster V, Sweeny JM. Aspirin: a historical and contemporary therapeutic overview. Circulation. 2011 Feb 22;123(7):768-78.
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Consumer Information

How It Works

Bottom Line: Willow bark is useful in relieving muscle and joint pain.

Willow bark is commonly used to treat pain and reduce fevers. It contains a compound called salicin that has been shown to have anti-inflammatory effects. Aspirin is the synthetic form of acetylsalicylic acid, which is derived from salicin. Several studies have shown that willow bark extracts are effective in reducing back pain and osteoarthritis. Long term use of low-dose aspirin has been shown to prevent heart attacks.
Observational studies suggest that aspirin may help in lowering the risk of some cancers. It is not known if willow bark supplements will have the same effects.

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Purported Uses
  • To reduce fever
    Willow bark is thought to act in the same way as aspirin, but clinical trials have not been performed.
  • To treat pain, including muscle pain and headaches
    Clinical trials have shown that willow bark extract is effective in treating low back pain, and can reduce the pain of osteoarthritis. Another clinical trial found that it could reduce pain in patients with gonarthritis (arthritis of the knee) and coxarthrosis (arthritis of the hip joint).
  • To treat and prevent heart disease
    Several studies show that long-term use of low-dose aspirin is effective in preventing heart attacks.
  • To prevent cancer
    Epidemiologic data indicate that aspirin is useful in reducing risk of certain cancers. Clinical trials have not been done.
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Research Evidence

Gonarthrosis
In this open, multi-centric study, 88 patients, ages between 50 and 75, with gonarthrosis and coxarthrosis were treated with a standardized willow bark extract, and 40 patients with standard therapy. Effectiveness of the treatments was determined by clinical findings, recording of adverse events, global tolerance and by patient assessment (WOMAC questions concerning pain and stiffness, questions on general state of health). After 6 weeks, researchers reported that the willow bark extract was better than conventional therapy. It was also well tolerated with no adverse effects.

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Do Not Take If
  • You are taking warfarin or other blood thinners (willow bark may increase the risk of bleeding).
  • You are taking non-steroidal anti-inflammatory drugs (NSAIDs) (willow bark may increase the risk of stomach and intestinal damage and bleeding).
  • You are allergic to aspirin.
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Side Effects
  • Willowbark supplements can cause allergic reactions and can affect platelet aggregation.
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Special Point
  • Children should not be given willow bark because of the potential for developing Reye syndrome, a serious condition associated with the use of aspirin.
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Last updated: May 30, 2013
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