White willow's therapeutic uses

DEFINITION: Natural plant product used to treat specific health conditions.

PRINCIPAL PROPOSED USES: Back pain, bursitis, dysmenorrhea, migraine headaches, musculoskeletal pain, osteoarthritis, rheumatoid arthritis, tendonitis, tension headaches, anti-inflammatory, fever

Overview

Willow bark has been used to treat pain and fever in China since 500 Before the Common Era. In Europe, it was primarily used for altogether different purposes, such as stopping vomiting, removing warts, and suppressing sexual desire. However, in 1828, European chemists made a discovery that would bring together some of these different uses. They extracted the substance salicin from white willow, which was soon purified to salicylic acid. Salicylic acid is an effective treatment for pain and fever, but it is also sufficiently irritating to do a good job of burning off warts. Chemists later modified salicylic acid (this time from the herb meadowsweet) to create acetylsalicylic acid, or aspirin.

Therapeutic Dosages

Standardized willow bark extracts should provide 120 to 240 milligrams (mg) of salicin daily.

Therapeutic Uses

As interest in natural medicine grew, many people have begun to turn to white willow as an alternative to aspirin. One double-blind, placebo-controlled trial found it effective for back pain, and another found it helpful for osteoarthritis. White willow is also used for such conditions as bursitis, dysmenorrhea, tension headaches, migraine headaches, rheumatoid arthritis, and tendonitis. However, two recent studies failed to find it effective for rheumatoid arthritis or osteoarthritis. White willow is used less often as a fever reducer and for its antioxidant and immune-boosting properties.

Aspirin and related anti-inflammatory drugs are notorious for irritating or damaging the stomach. However, when taken in typical doses, willow does not appear to produce this side effect to the same extent. This may be partly because most of the salicylic acid provided by white willow comes from salicin and other chemicals that are converted to salicylic acid only after absorption into the body. Other evidence suggests that standard doses of willow bark are the equivalent of one baby aspirin daily, rather than a full dose.

This latter finding raises an interesting question: How can it work if willow provides only a small amount of salicylic acid? The most likely answer is that other constituents besides salicin play a role. Another possibility is that the studies finding benefit were flawed and that it actually does not work.

Scientific Evidence

In a four-week, double-blind, placebo-controlled study of 210 individuals with back pain, two doses of willow bark extract were compared against placebo. The higher-dose group received an extract supplying 240 mg of salicin daily; in this group, 39 percent were pain-free for at least five days of the last week of the study. In the lower-dose group (120 mg of salicin daily), 21 percent became pain-free. In contrast, only 6 percent of those given a placebo became pain-free. Stomach distress did not occur in this study. The only significant side effect seen was an allergic reaction in one participant who was given willow. Benefits were also seen in a double-blind, placebo-controlled trial of seventy-eight individuals with knee or hip osteoarthritis.

However, two subsequent double-blind, placebo-controlled studies performed by a single research group failed to find white willow more effective than placebo. One enrolled 127 people with osteoarthritis (OA) of the hip or knee, and the other 26 outpatients with active rheumatoid arthritis (RA). In the OA trial, participants received either willow bark extract (240 mg of salicin per day), the standard drug diclofenac (100 mg per day), or placebo. In the RA trial, participants received either willow bark extract at the same dose or placebo. While diclofenac proved significantly more effective than placebo in the OA trial, willow bark did not. It also failed to prove more effective than placebo in the RA study. A 2020 pilot study also failed to find any benefit to participants who were given white willow to prevent delayed-onset muscle soreness following resistance training. The most likely interpretation of these conflicting findings is that willow provides, at best, no more than a modest level of pain relief.

Safety Issues

Evidence suggests that willow, taken at standard doses, is the equivalent of 50 mg of aspirin, a very small dose. Willow does not impair blood coagulation to the same extent as aspirin, and it does not appear to irritate the stomach significantly. Nonetheless, it seems reasonable to suppose that if it is used over the long term or in high doses, willow could still cause the side effects associated with aspirin. All the risks of aspirin therapy potentially apply.

For this reason, children should not be given white willow because of the risk of Reye’s syndrome. It should also not be used by people with aspirin allergies, bleeding disorders, or kidney disease. In addition, white willow may interact adversely with blood thinners, other anti-inflammatory drugs, methotrexate, metoclopramide, phenytoin, probenecid, spironolactone, and valproate. Safety in pregnant or nursing women or in those with severe liver or kidney disease has not been established.

Important Interactions

Persons should avoid combining white willow with blood-thinning medications such as warfarin (Coumadin), heparin, clopidogrel (Plavix), ticlopidine (Ticlid), and pentoxifylline (Trental). White willow should also not be taken with aspirin, methotrexate, metoclopramide, phenytoin (Dilantin), sulfonamide drugs, spironolactone and other potassium-sparing diuretics; or with valproic acid.

Bibliography

Biegert, C., et al. "Efficacy and Safety of Willow Bark Extract in the Treatment of Osteoarthritis and Rheumatoid Arthritis." Journal of Rheumatology, vol. 31, 2004, pp. 2121-2130.

Cheshier, Brandie Cai, et al. "Effect of White Willow Bark on Delayed Onset Muscle Soreness Following Resistance Training: A Pilot Study." The Asian Journal of Kinesiology, vol. 23, no. 4, 31 Oct. 2021, pp. 40-49, doi.org/10.15758/ajk.2021.23.4.40. Accessed 15 Sept. 2024.

Synovitz, Linda B., and Karl L. Larson. Consumer Health and Integrative Medicine: Holistic View of Complementary and Alternative Medicine Practices. 2nd ed., Jones & Bartlett Learning, 2020.

Uehleke, B., et al. "Willow Bark Extract STW 33-I in the Long-Term Treatment of Outpatients with Rheumatic Pain Mainly Osteoarthritis or Back Pain." Phytomedicine, vol. 20, no. 11, 2013, pp. 980-984.

"Willow Bark." Icahn School of Medicine at Mount Sinai, www.mountsinai.org/health-library/herb/willow-bark. Accessed 15 Sept. 2024.

Wilson, Debra Rose, and SaVanna Shoemaker. "Willow Bark: Nature's Aspirin." Healthline, 9 Jan. 2017, www.healthline.com/health/willow-bark-natures-aspirin. Accessed 15 Sept. 2024.