Willow bark comes from the willow tree of the Salix species. The bark contains salicin, a compound similar to aspirin. Salicin is metabolized in the body to create salicylic acid, a precursor to aspirin.
Health Benefits Willow bark's analgesic (pain-relieving) and antipyretic (fever-reducing) properties have been touted since as far back as 4th-century Greece.
Salicin, when converted to salicylic acid, inhibits the activity of cyclo-oxygenase 1 (COX-1) and cyclo-oxygenase 2 (COX-2). These are the same enzymes targeted by NSAIDs to alleviate pain and inflammation.
Alternative practitioners contend that willow bark can safely treat a host of pain disorders, including headache, low back pain, knee pain, osteoarthritis, and rheumatoid arthritis.
Possible Side Effects: Willow bark is considered safe for short-term use. Insofar as willow bark similar to aspirin, it is possible to develop many of the same side effects, particularly if overused. These may include stomach upset, vomiting, dizziness, gastrointestinal bleeding, liver toxicity. Children and teens should not use willow bark due to a rare but potentially fatal condition known as Reye's syndrome, commonly associated with aspirin. The same applies to breastfeeding mothers who may inadvertently transmit salicin to their babies. The safety of willow bark during pregnancy is unknown, so it is best to avoid it if you are pregnant or planning to get pregnant. An allergic response to willow bark is also possible, especially in those with a known allergy to aspirin.
Drug Interactions: Willow bark may slow blood clotting and prolong bleeding time. As such, it should not be taken with anticoagulants like Coumadin (warfarin), antiplatelet drugs like Plavix (clopidogrel), or any drugs associated with bleeding (including NSAIDs). For the same reason, you would need to stop taking willow bark two weeks before scheduled surgery to avoid excessive bleeding. Willow bark should also not be used in hemophiliacs or people with other bleeding disorders.
There are no guidelines directing the appropriate use of willow bark. Generally speaking, oral doses of up to 400 mg per day are considered safe and effective for the short-term treatment of muscle or joint pain.