Plant Description

The willow family includes a number of different species of trees and shrubs native to Europe, Asia, and some parts of North America. Some of the more commonly known species are white willow/European willow ( Salix alba ), black willow/pussy willow ( Salix nigra ), crack willow ( Salix fragilis ), purple willow ( Salix purpurea ), and weeping willow ( Salix babylonica ). Not all willow species accumulate a therapeutically sufficient amount of salicin. In one study, the amount of salicin after 1 and 2 year growth in autumn and spring ranged from 0.08 to 12.6%. The willow bark sold in Europe and the United States usually includes a combination of the bark from white, purple, and crack willows.

Medicinal Uses and Indications

Willow bark is used to ease pain and reduce inflammation. Researchers believe that the chemical salicin, found in willow bark, is responsible for these effects. However, studies show several other components of willow bark, including plant chemicals called polyphenols and flavonoids, have antioxidant, fever-reducing, antiseptic, and immune-boosting properties. Some studies show willow is as effective as aspirin for reducing pain and inflammation (but not fever), and at a much lower dose. Scientists think that may be due to other compounds in the herb. More research is needed.

Treatment

Studies suggest that willow bark may be useful for the following conditions:

Headache

Willow bark has been shown to relieve headaches. There is some evidence that it is less likely to cause gastrointestinal side effects than other pain relievers, such as ibuprofen (Advil) and other nonsteroidal anti-inflammatory drugs, do. However, studies have not shown this beyond all doubt, and people who are prone to stomach upset may want to avoid willow bark. Large-scale studies are needed to fully determine how safe and effective willow bark is for chronic or recurring headaches.

Low back pain

Willow bark appears to be effective for back pain. In a well-designed study of nearly 200 people with low back pain, those who received willow bark experienced a significant improvement in pain compared to those who received placebo. People who received higher doses of willow bark (240 mg salicin) had more significant pain relief than those who received low doses (120 mg salicin).

Osteoarthritis

Several studies show that willow is more effective at reducing pain from osteoarthritis than placebo. In a small study of people with osteoarthritis of the neck or lower back, those who received willow bark experienced significant improvement in symptoms compared to those who received placebo. A similar study of 78 people hospitalized with osteoarthritis of the knee or hip joint found that people who received willow bark had significant pain relief compared to those who received placebo.

Other uses

Professional herbalists may recommend willow bark for the following conditions, however, more research is needed.

• Menstrual cramps
• Fever
• Flu
• Tendonitis
• Bursitis
• Cancer

Dosage and Administration

Pediatric

Because of the danger of developing Reye syndrome (a rare but serious illness associated with the use of aspirin in children), children under the age of 18 should not take willow bark.

Adult

Speak to your doctor to determine the appropriate dose for you.

Precautions

Because willow bark contains salicin, people who are allergic or sensitive to salicylates (such as aspirin) should not use willow bark. Some researchers suggest that people with asthma, diabetes, gout, gastritis, hemophilia, stomach ulcers, or with kidney or liver issues should also avoid willow bark. If you have any of these conditions, or if you take nonsteroidal anti-inflammatory drugs (NSAIDs) or blood-thinning medication, ask your health care provider before taking willow bark. Children under the age of 16 should not take willow bark.

Side Effects

Side effects tend to be mild. However, stomach upset, ulcers, nausea, vomiting, and stomach bleeding are potential side effects of all compounds containing salicylates. Overdoses of willow bark may cause skin rash, stomach inflammation/irritation, nausea, vomiting, kidney inflammation, and tinnitus (ringing in the ears).

Pregnancy and Breastfeeding

Salicylates are not recommended during pregnancy, so pregnant and breastfeeding women should not take willow bark.

Interactions and Depletions

Because willow bark contains salicylates, it might interact with a number of drugs and herbs. Talk to your doctor before taking willow bark if you take any other medications, herbs, or supplements.

Willow bark may interact with any of the following:

Anticoagulants (blood-thinning medications): Willow bark may strengthen the effects of drugs and herbs with blood-thinning properties, and increase the risk of bleeding.

Beta blockers: including Atenolol (Tenormin), Metoprolol (Lopressor, Toprol-XL), Propranolol (Inderal, Inderal LA). Willow bark may make these drugs less effective.

Diuretics (water pills): Willow bark may make these drugs less effective.

Nonsteroidal anti-inflammatory drugs: including ibuprofen (Advil, Motrin) and naproxen (Aleve). Taking willow bark with these drugs may increase risk of stomach bleeding.

Methotrexate and phenytoin (Dilantin): Willow bark may increase levels of these drugs in the body, resulting in toxic levels.

Supporting Research

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Chrubasik S, Eisenburg 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.

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