Willow bark is a herbal drug. Its active ingredient is salicin, which can decrease the production
in the nerve endings of those chemical elements that cause pain. Limited evidence tells that
willow bark may have a moderate effect in reducing pain caused by rheumаtoid arthritis and
osteoarthritis. In one study, comparing it with nonsteroidal anti-inflammatory drugs, it was
concluded that willow bark has a low efficacy in osteoarthritis.
It's worth to mention, willow bark contains a component called salicin, which your body converts into another chemical substance called salicylic acid. Like acetylsalicylic, salicylic acid decreases the production of certain prostaglandins (hormone-like substances that control your immune system and fight joint inflammation) in your nerves, which relieves pain. The willow bark showed anti-inflammatory activity in several laboratory studies.
Two randomized controlled studies have shown the effectiveness of willow bark in the treatment of osteoarthritis of the knee and hip joints. Willow bark was well tolerated by subjects who participated in both randomized clinical trials. Lack of effectiveness has become the most common reason for not using this drug widely.
In the first trial test, 127 participants were randomly separated into groups to receive willow bark (240 mg salicin), 100 mg diclofenac (a non-steroidal anti-inflammatory drug) or placebo for 6 weeks on a daily basis.
In the second test, 78 people took part. These participants were divided into groups that took willow bark or placebo every day for 2 weeks. Participants who took willow bark reached a 14% reduction in pain by the conclusion of the trial, and those who took the placebo pill had pain decreased by 2%.