Comprehensive Guide to White Willow Bark
(Salix spp)

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White Willow BarkDr. James Meschino DC, MS, ND
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General Features
The white willow tree is native to North America and central and southern Europe. Both the bark and leaves contain the active constituents (phenolic glycosides), although the bark has been used traditionally in the preparation of the medicinal white willow extract.1,2 Willow bark has been used as a treatment for fever and pain in China since 500 BC. One of the principle active constitutents in White Willow Bark is salicin or salicylic acid. Its discovery in the nineteenth century led to the development of aspirin, which is a synthetic version of this phenolic glycoside, known as acetylsalicylic acid (ASA), produced from the chemical modification of salicylic acid.11,14 There are some distinct differences between the physiological action of ASA and salicin that indicate that salicin may be safer to use under certain conditions, as it does not impair blood clotting to the same degree as aspirin, and it does not appear to significantly irritate the stomach lining.12,13 The analgesic effects of white willow extract are slower to develop than that of ASA, but may last longer than the analgesic effects of aspirin.
Principle Active Constituents

1. Phenolic glycosides including salicin, salicortin, tremulacin and salireposide.
2. Other constituents include tannins, flavonoids and catechins

Clinical Application and Mechanism of Action
1. Anti-inflammatory and Pain Killer (Analgesic) Effects
White Willow Bark (100 mg) in conjunction with other herbal agents has been shown to be effective in the management of osteoarthritis, with respect to reduced pain and improved joint function.5
The pharmacological action of willow appears to be largely determined by its salicin content, although other phenolic glycosides within white willow extract have also been shown to have anti-inflammatory properties. 6,7,18
The phenolic glycosides (including salicin) from white willow extract are slowly converted into active moieties (most notably salicylic acid), primarily in the liver and intestines, via a multiple stage process.7 Like aspirin, these active moieties inhibit the synthesis of inflammatory prostaglandin hormones that are involved in inflammatory conditions and the production of pain and fever. 1,7,17
However, as the phenolic glycosides in white willow extract are converted by the body slowly into various active anti-inflammatory moieties, the biological effect is, therefore, slower than conventional ASA use, but has been shown in some studies to have a longer duration of action.
It should be noted that salicin, from White Willow Bark extract, does not irreversibly inhibit platelet aggregation in contrast to the effects of acetylsalicylic acid (ASA).7 Thus, white willow extract is not considered to be a strong anticoagulant and may therefore, be an acceptable alternative anti-inflammatory and pain killer medications in cases where the anticoagulant effects of ASA and other non steroidal anti-inflammatory drugs (eg., ibuprofen) are contraindicated. 7
Back Pain: A four week double-blind placebo-controlled trial, published in the American Journal of Medicine (2000), showed that white willow extract demonstrated almost a 40% success rate in regards to helping low back pain patients achieve a pain-free state, compared with only a 6% success rate in the placebo group. In this group of 210 low back pain patients, none of the white willow extract users reported any stomach pain or gastrointestinal intolerance of any type. One patient within the white willow extract group had an allergic reaction.
Osteoarthritis: A double-blind placebo-controlled trial of 78 subjects with osteoarthritis of the knee or hip also showed that white willow extract was effective in decreasing pain and improving joint function compared to the placebo.1
2. Headache
Some evidence suggests that White Willow Bark extract may be helpful in the treatment of certain headaches.
Dosage and Standardized Grade
Arthritis, Back Pain, and Headaches: If taken as a single agent, a daily dose of salicin totaling 60 to 120 mg (taken in divided doses) is commonly recommended. 15 However, in the clinical trials cited above, daily doses as high as 120 to 240 mg of salicin were used successfully.11,15,16,17 Note that most standardized white willow products contain 15% salicin content, thus 100 mg of white willow extract at a standardized grade of 15%, salicin, would yield 15 mg of salicin.
Often, White Willow Bark extract (100 mg, 15% standardized grade of salicin content) is combined with other anti-inflammatory herbs for therapeutic use.
Adverse Side Effects, Toxicity and Contraindications
Due to the presence of salicin, some researchers suggest that White Willow Bark extract is contraindicated for conditions that also involve contraindications to ASA. These include asthma, diabetes, gout, haemophilia, hyperthrombinaemia, hepatic / renal disease, active peptic ulcer disease, glucose - 6 - phosphate dehydrogenase deficiency, individuals sensitive to aspirin and children under 12 years of age. 3 According to the Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines, the most well established contraindications include active peptic ulcers, gastritis, and children under 12 years of age.9 When taken at standard doses (120 mg per day of salicin content), white willow extract is the equivalent of 50 mg of aspirin (a baby aspirin), which is a very small dose (one regular aspirin contains 300 to 320 mg of acetylsalicylic acid). As such, experts have concluded that other active constituents (eg., other phenolic glycosides) also play a role in the anti-inflammatory and pain-relieving effects associated with the use of white willow extract. 16 Like aspirin, white willow extract also provides an analgesic effect, helping to reduce pain. 11 Some occasional gastrointestinal upset and allergic reactions occur with the use of white willow extract, but the incidence of stomach upset and intestinal distress are significantly less than occurs with use of aspirin, which is notorious for is effects on causing erosion and ulcerations to the gastrointestinal tract.9,11,13 Nausea and headaches are also rare side effects associated with the use of white willow extract

Drug-Nutrient Interactions
White Willow Bark extract may interact with other drugs in a similar fashion as ASA, producing a negative health effect. Although no reports of White Willow Bark extract have been reported practitioners should be alerted to the following potential drug-nutrient interactions with salicin:
Drug Combined Effect
Acebutoiol Decreased anti-hypertensive effect of acebutoiol
Adrenocorticoids (systemic) Increased adrenocorticoid effect
Alendronate (biphosphanate) Increased risk of stomach irritation if taken within 30 minutes of Alendronate
Allopurinol Decreased allopurinol effect by increasing kidney resorption of uric acid
ACE Inhibitor Decreased ACE inhibitor effect (angiotensin–converting enzyme) -anti-hypertensive drugs
Antacids Decreased aspirin effect
Anticoagulants Increased anti-coagulant effect (abnormal bleeding)
Anti-diabetic agents (oral) Low blood sugar
Anti-inflammatory drugs (NSAIDs) Risk of stomach, intestinal bleeding and ulcers
Bumetanide Possible aspirin toxicity
Carteolol Decreased anti-hypertensive effect of carteolol
Pregnancy and Lactation
During pregnancy and lactation, the only supplements that are considered safe include standard prenatal vitamin and mineral supplements. All other supplements or dose alterations may pose a threat to the developing fetus and there is generally insufficient evidence at this time to determine an absolute level of safety for most dietary supplements other than a prenatal supplement. Any supplementation practices beyond a prenatal supplement should involve the cooperation of the attending physician (e.g., magnesium and the treatment of preeclampsia.)

References:Pregnancy and Lactation
1. Encyclopedia of Nutritional Supplements. Murray M. Prima Publishing 1998.
2. Reavley NM. The New Encyclopedia of Vitamins, Minerals, Supplements, and Herbs. Evans and Company Inc. 1998.
3. The Healing Power of Herbs (2nd edition). Murray M. Prima Publishing 1995.
4. Boon H and Smith M. Health Care Professional Training Program in Complementary Medicine. Institute of Applied Complementary Medicine Inc. 1997.
References
1. Bradley PR, et.al., British Herbal Compendium, Vol.1, Bournemouth, Dorset, UK, British Herbal Medicine Association 1992, 224-226
2. Meier B, et.al., Pharmaceutical Aspects of the Use of Willows in Herbal Remedies, Planta Medica, 54, 1988, 559-560.
3. Newall C, Anderson L, Phillipson J, Herbal Medicines. A Guide for Health Care Professionals, London: The Pharmaceutical Press, 1996, 296.
4. Meier B, et.al., Identifikation und Bestimmung Von Je Acht Phenolglykosiden in Salix Purpurea und Salix Daphnoides Mit Moderner HPLC, Pharmaceutica Acta Helvetica 60, 1985, 269-274.
5. Mills SY, et.al., Effect of a Proprietary Herbal Medicine on the Relief of Chronic Arthritic Pain: A Double-blind Study, Br J Rheum, 35, 1996, 874-878.
6. Tyler V, Herbs of Choice. The Therapeutic Use of Phytomedicinals, Binghampton: Pharmaceutical Products Press, 1994, 209.
7. ESCOP, Salicis Cortex/Willow Bark, In: ESCOP Monograph Fascicule 4 Exeter, ESCOP, 58, 1997.
8. Hoffmann D, Holistic Herbal, Rockport, CA: Element Books, 1996, 256.
9. Blumenthal M, et.al., The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines, Boston, MA: Integrative Medicine Communications, 1998, 230.
10. Griffith HW, Complete Guide to Non Prescription and Prescription Drugs, The Body Press / Perigee, 1998, 132-133.
11. Natural Products Encylopedia. http://www.consumerslab.com/: White Willow
12. Krivoy N, Pavlotsky E, Chrubasik S et al. Effect of Salicic cortex extract on human platelet aggregation. Planta med 2000;66:1-4
13. European Scientific Cooperative on Phytotherapy. Salicis cortex. Exeter UK: ESCOP; 1996-1997:p2. Monographs on the medicinal uses of plant drugs, fascicule 4.
14. Foster S. 1010 Medicinal Herbs. Interweave Press, Loveland CO 1998:210-1
15. Healthnotes Inc. 2001. www.healthnotes.com: Willow
16. 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
17. 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 [translated from German.] Z Rheumatol 2000;59:314-20
18. Weiss RF. Herbal Medicine. Ab Arcanum, Gothenburg, Sweden 1988;31:p303
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