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Willow bark (Salix spp.)

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Also listed as: Salix spp., Salicin
Related terms
Background
Evidencetable
Tradition
Dosing
Safety
Interactions
Attribution
Bibliography

Related Terms
  • 2-(hydroxymethyl)phenyl-beta-D-glucopyranoside, acetylsalicylic acid, acid, aromatic aldehyde, aspirin, Assalix®, Assplant®, basket willow, bay willow, beta-salicin, black willow, brittle willow, cadmium, caffeic acid, cortza de sauce, crack willow, daphne willow, ecorce de saule (French), ethanolic salic extract 1520L, ferulic acid, flavonoids, fragilin, glycosides, isosalicin, isosalipurposide, knackweide, laurel willow, lorbeerweide, naringenin-7-O-glucoside, osier rouge, picein, polyphenols, populin, purple osier, purple osier willow, purple willow, purpurweide, reifweide, Reumalex®, rheumakaps, rutin, Salicaceae (family), salice (Italian), salicin, salicis cortex, salicortin, salicoylsalicin, salicyl alcohol, salicylate, salicylic acid, salicyluric acid, salidroside, saligenin, salipurposide, salix, Salix alba, Salix alba L., Salix daphnoides, Salix dasyclados L., Salix fragilis L., Salix mollissima L., Salix pentandra, Salix purpurea L., Salix triandra L., Salix viminalis "Americana", sauce (Spanish), standardized willow bark extract (STW 33-I), syringin, tannins, tremulacin, triandrin, vanillin, violet willow, weidenrinde (German), white willow, white willow bark, willow, willow bark, willow tree, willowbark, willowprin.
  • Note: This review covers salicin-containing species of Salix, which includes Salix alba, Salix fragilis, Salix purpurea, and Salix pentandra. Additionally, salicin and salicylates are present not only in willow, but also other Salicaceae family plants such as poplar (several different Populus genus members), as well as completely different plant family members, such as birch (Betula spp; Betulaceae family), and meadowsweet (Filipendula ulmaria; Rosaceae family). These compounds are not specific to just willow. Although salicylates are discussed in this monograph they are not the focus of this monograph.

Background
  • In the United States, willow bark is used by herbalists as a fever reducer, a mild pain reliever, and an anti-inflammatory. There is evidence that supports willow bark use for osteoarthritis and lower back pain. Early study suggests that willow bark extracts may not be helpful for rheumatoid arthritis, but further study is needed to form strong conclusions. Taking willow bark may increase the risk of bleeding; however, this risk may be less than taking aspirin.
  • Several countries in Europe have approved willow bark for pain and inflammatory disorders. The German Commission E has approved willow bark for fever, rheumatic ailments, and headaches. The British Herbal Compendium indicates that willow bark can be used for rheumatic and arthritic conditions, and fever associated with cold and influenza. In France, willow bark has been approved as a pain reliever to treat headache and toothache pain, as well as painful articular (joint) conditions, tendonitis, and sprains. The European Scientific Cooperative on Phytotherapy (ESCOP) has approved willow bark extract for the treatment of fever, pain, and mild rheumatic complaints.
  • Willow bark contains salicylates that may present a safety risk to people, specifically those with aspirin allergy or sensitivity, those using blood thinners, and children with flu-like symptoms due to Reye's syndrome.

Evidence Table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *


Willow bark has been studied for its effects in the treatment of lower back pain. Studies have found willow bark to be as effective to other methods. Cost effectiveness studies have also found that willow bark was cost effective. Due to the small number of studies available, further research is needed to confirm willow bark's efficacy for lower back pain.

B


Willow bark has been used to treat many types of inflammatory conditions, including headache. One study investigated a salicin topical cream for the treatment and/or prevention of migraine and tension-type headache. Although early study is promising, additional study is needed to form any firm conclusions.

C


Willow bark is a traditional pain relieving agent for osteoarthritis. Several studies have found mixed results. Additional research is needed in this area before any firm conclusions can be made.

C


Based on limited available evidence, willow bark extract lacks an effect in the treatment of rheumatoid arthritis (RA). Additional study is needed to make a firm conclusion.

C


Use of a combination product containing will bark resulted in increased weight loss over placebo. However, more clinical research is needed before any firm conclusions can be made.

C
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)


Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

  • Analgesic (pain relief), ankylosing spondylitis (long-term arthritis), anti-inflammatory, antioxidant, antiplatelet, antiseptic, antiviral, asthma, cancer, colds, connective tissue disorders, coronary artery disease prevention, diabetes, fever, gout, inflammatory bowel disease, malaria, menstrual cramps, sore throat, sprains, tendonitis (inflammation of tendon), toothache, warts.

Dosing

Adults (18 years and older)

  • According to secondary sources, the German Commission E recommends doses of willow bark extract of 60-120 milligrams of total salicin (active ingredient) daily.
  • For lower back pain, 120-240 milligrams of willow bark extract have been taken by mouth daily for four weeks. In addition, 1,573-1,600 milligrams of willow bark have been taken by mouth daily for 2-6 weeks.
  • For osteoarthritis, 1,360-2,160 milligrams of willow bark extract containing 240 milligrams of salicin have been taken by mouth daily for up to six weeks. Additionally, a willow bark extract containing 120 milligrams of salicin has been taken by mouth twice daily for six weeks. Coated tablets containing 1,360-2,160 milligrams of willow bark extract have been taken by mouth daily for two weeks.
  • For rheumatoid arthritis, willow bark extract containing 120 milligrams of salicin has been taken twice daily for six weeks.

Children (younger than 18 years)

  • There is no proven safe or effective dose for willow bark in children.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

  • Avoid with known allergy or sensitivity to aspirin, willow bark (Salix species.), or any of its parts, including salicylates.

Side Effects and Warnings

  • Willow bark is likely safe when used under the supervision of a health care professional and in doses of 120-240 milligrams of salicin for up to six weeks.
  • Willow bark may alter blood pressure. Caution is advised in people taking drugs or herbs and supplements that affect blood pressure.
  • Willow bark may increase the risk of bleeding. Caution is advised in people with bleeding disorders or taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.
  • Willow bark may also cause anemia, black stool, constipation, diarrhea, dizziness, fatigue, headache, heartburn, heat sensation, increased triglyceride levels, increased uric acid in blood, increased cadmium levels, indigestion, itching, kidney disorder, liver dysfunction, rash, stomach bleeding, stomach pain, swollen eyes, vomiting, vomiting blood, and weakness.
  • Use caution in combination with agents such as carbonic anhydrase inhibitors (acetazolamide), beta-blockers, barbiturates, diuretics, ephedrine, methotrexate, phenytoin, probenecid, protein-bound agents, spironolactone, sulfinpyrazone, sulfonylureas, valproic acid, or caffeine, due to the potential of increased adverse events.
  • Use caution in people with iron deficiency due to a report of anemia.
  • Use caution in people with stomach and intestine problems, as well as in those using agents that increase the risk of stomach bleeding because willow bark may cause stomach and intestine side effects.
  • Use caution in people with skin concerns due to reports of adverse effects.
  • Use caution in people with asthma or diabetes.
  • Use caution in people with gout, due to the small amount of salicylate present in while willow bark, which may cause high uric acid in the blood.
  • Use caution in people at risk of ringing ears based on suggestions that ringing ears is a known symptom of salicylate overdose.
  • Use caution in people with eye concerns as swollen eyes were reported in a clinical study.
  • Use caution in people with frequent headaches, as willow bark may cause severe headaches.
  • Use caution when taking willow bark with tannin-containing herbs or supplements, as this combination may affect the absorption of salicylic acid (part of willow bark).
  • Use caution in people requiring concentration or using heavy machinery, as willow bark may cause dizziness.
  • Avoid use in children with chickenpox and any other viral infections because of association between salicylates and Reye's syndrome.
  • Avoid use in people with liver or kidney disorders, or heart failure, based on information suggesting that willow bark may worsen these conditions.
  • Avoid use in pregnant women, as salicylates are listed as a pregnancy category D (positive evidence of human fetal risk with use).
  • Avoid use in breastfeeding women due to reports of salicylates in breast milk and toxic effects in infants following aspirin use by the mother.
  • Avoid use in people with high cadmium levels, as willow may contain high levels of cadmium.
  • Avoid with known allergy or sensitivity to aspirin, willow bark (Salix species.), or any of its parts, including salicylates.

Pregnancy and Breastfeeding

  • Avoid use in pregnant women, as salicylates are listed as a pregnancy category D (positive evidence of human fetal risk with use).
  • Avoid use in breastfeeding women due to reports of salicylates in breast milk and toxic effects in infants following aspirin use by the mother.

Interactions

Interactions with Drugs

  • Willow bark may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
  • Willow bark may alter blood pressure. Caution is advised in people taking drugs that affect blood pressure.
  • Willow bark may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
  • Willow bark may increase the amount of drowsiness caused by some drugs. Examples include benzodiazepines such as lorazepam (Ativan®) or diazepam (Valium®), barbiturates such as phenobarbital, narcotics such as codeine, some antidepressants, and alcohol. Caution is advised while driving or operating machinery.
  • Willow bark may also interact with acetazolamide, agents for fever, agents for gout, agents for pain, agents for the eyes, agents for the skin, agents that increase urine, alcohol, anti-inflammatories, appetite stimulants, barbiturates, beta-blockers, caffeine, cancer agents, carbonic anhydrase inhibitors, ephedrine, heparin, iron, kidney agents, liver toxins, methotrexate, nervous system agents, nonsteroidal anti-inflammatory agents, phenytoin, probenecid, protein-bound agents, salicylates, spironolactone, stomach and intestine agents, sulfinpyrazone, sulfonylureas, sun sensitizing agents, valproic acid, warfarin, and weight loss agents.

Interactions with Herbs and Dietary Supplements

  • Willow bark may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
  • Willow bark may alter blood pressure. Caution is advised in people taking drugs that affect blood pressure
  • Willow bark may also interact with, anti-inflammatories, antioxidants, appetite stimulants, black cohosh, cadmium, caffeine, cancer herbs and supplements, ephedra, guaiacum resin, herbs and supplements for fever, herbs and supplements for gout, herbs and supplements for pain, herbs and supplements that increase urine, iron, kidney herbs and supplements, liver herbs and supplements, nervous system herbs and supplements, poplar bark, protein-bound herbs and supplements, salicylates, sarsaparilla, stomach and intestine herbs and supplements, sun sensitizing herbs and supplements, tannin-containing herbs and supplements, and weight loss herbs and supplements.

Attribution
  • This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography
  1. Baker S, Thomas PS. Herbal medicine precipitating massive haemolysis. Lancet 5-2-1987;1(8540):1039-1040.
  2. Biegert C, Wagner I, Ludtke R, et al. Efficacy and safety of willow bark extract in the treatment of osteoarthritis and rheumatoid arthritis: results of 2 randomized double-blind controlled trials. J.Rheumatol. 2004;31(11):2121-2130.
  3. Chrubasik S, Künzel O, Model A, et al. Assalix® vs. Vioxx® for low back pain - a randomised open controlled study. 8th Annual Symposium on Complementary Health Care, 6th - 8th December 2001 2001.
  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(1):9-14.
  5. Chrubasik S, Kunzel O, Black A, et al. Potential economic impact of using a proprietary willow bark extract in outpatient treatment of low back pain: an open non-randomized study. Phytomedicine 2001;8(4):241-251.
  6. Chrubasik S, Kunzel O, Model A, et al. Treatment of low back pain with a herbal or synthetic anti-rheumatic: a randomized controlled study. Willow bark extract for low back pain. Rheumatology (Oxford) 2001;40(12):1388-1393.
  7. Edwards JE, Oldman A, Smith L, et al. Single dose oral aspirin for acute pain. Cochrane Library 2002;1.
  8. Eisenberg E, Chrubasik S, Balan E, et al. Willow bark extract for low back pain: a randomised double-blind study. Focus on Alternative and Complementary Therapies 2002;7(1):91-92.
  9. Ernst E, Chrubasik S. Phyto-anti-inflammatories. A systematic review of randomized, placebo- controlled, double-blind trials. Rheum Dis Clin North Am 2000;26(1):13-27, vii.
  10. Gagnier JJ, van Tulder M, Berman B, Bombardier C. Herbal medicine for low back pain. Cochrane Database.Syst.Rev 2006;(2):CD004504.
  11. Hyson MI. Anticephalgic photoprotective premedicated mask. A report of a successful double-blind placebo-controlled study of a new treatment for headaches with associated frontalis pain and photophobia. Headache 1998;38:475-477.
  12. Little CV, Parsons T, Logan S. Herbal therapy for treating osteoarthritis. The Cochrane Library 2002;1.
  13. Marson P, Pasero G. [The Italian contributions to the history of salicylates]. Reumatismo. 2006;58(1):66-75.
  14. Schmid B, Ludtke 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(4):344-350.
  15. Schmid B, Ludtke R, Selbmann HK, et al. [Effectiveness and tolerance of standardized willow bark extract in arthrosis patients. Randomized, placebo controlled double-blind study]. Z Rheumatol 2000;59(5):314-320.

Copyright © 2011 Natural Standard (www.naturalstandard.com)


The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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