Herbal medications commonly used in the practice of rheumatology: mechanisms of action, efficacy, and side effects

OBJECTIVE: To review the literature on herbal preparations commonly utilized in the treatment of rheumatic indications. METHODS: Search of MEDLINE (PubMed) was performed using both the scientific and the common names of herbs. Relevant articles in English were collected from PubMed and reviewed. RESULTS: This review summarizes the efficacy and toxicities of herbal remedies used in complementary and alternative medical (CAM) therapies for rheumatologic conditions, by elucidating the immune pathways through which these preparations have antiinflammatory and/or immunomodulatory activity and providing a scientific basis for their efficacy. Gammalinolenic acid suppresses inflammation by acting as a competitive inhibitor of prostaglandin E2 and leukotrienes (LTs) and by reducing the auto-induction of interleukin1alpha (IL-1alpha)-induced pro-IL-1beta gene expression. It appears to be efficacious in rheumatoid arthritis (RA) but not for Sjogrens disease. The antiinflammatory actions of Harpagophytum procumbens is due to its action on eicosanoid biosynthesis and it may have a role in treating low back pain. While in vitro experiments with Tanacetum parthenium found inhibition of the expression of intercellular adhesion molecule-1, tumor necrosis factor alpha (TNF-alpha), interferon-gamma, IkappaB kinase, and a decrease in T-cell adhesion, to date human studies have not proven it useful in the treatment of RA. Current experience with Tripterygium wilfordii Hook F, Uncaria tomentosa, finds them to be efficacious in the treatment of RA, while Urtica diocia and willow bark extract are effective for osteoarthritis. T. wilfordii Hook F extract inhibits the production of cytokines and other mediators from mononuclear phagocytes by blocking the up-regulation of a number of proinflammatory genes, including TNF-alpha, cyclooxygenase 2 (COX-2), interferon-gamma, IL-2, prostaglandin, and iNOS. Uncaria tomentosa and Urtica diocia both decrease the production of TNF-alpha. At present there are no human studies on Ocimum spp. in rheumatic diseases. The fixed oil appears to have antihistaminic, antiserotonin, and antiprostaglandin activity. Zingiber officinale inhibits TNF-alpha, prostaglandin, and leukotriene synthesis and at present has limited efficacy in the treatment of osteoarthritis. CONCLUSIONS: Investigation of the mechanism and potential uses of CAM therapies is still in its infancy and many studies done to date are scientifically flawed. Further systematic and scientific inquiry into this topic is necessary to validate or refute the clinical claims made for CAM therapies. An understanding of the mechanism of action of CAM therapies allows physicians to counsel effectively on their proper and improper use, prevent adverse drug-drug interactions, and anticipate or appreciate toxicities. RELEVANCE: The use of CAM therapies is widespread among patients, including those with rheumatic diseases. Herbal medications are often utilized with little to no physician guidance or knowledge. An appreciation of this information will help physicians to counsel patients concerning the utility and toxicities of CAM therapies. An understanding and elucidation of the mechanisms by which CAM therapies may be efficacious can be instrumental in discovering new molecular targets in the treatment of diseases.