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Complementary & Alternative Medicine
Index of Herbal Medicines, Supplements and Therapies
The decision to use products containing or claiming to contain cat's claw should be carefully considered.
Cat's Claw (Uncaria tomentosa, Uncaria guianensis)
Be aware that the U.S. Food and Drug Administration does not strictly regulate herbs and dietary supplements. There is no guarantee of strength, purity or safety of products containing or claiming to contain cat's claw. Decisions to use herbs or supplements should be carefully considered. Individuals using prescription drugs should discuss taking herbs or supplements with a pharmacist or health care professional before starting.
Scientists have studied cat's claw for the following health problems:
Several laboratory and animal studies suggest that cat's claw may reduce inflammation, and this has led to research of cat's claw for conditions that involve inflammation, such as rheumatoid arthritis. A small preliminary study demonstrates relative safety and modest benefit to tender joints using a highly purified extract from cat's claw in patients with active rheumatoid arthritis taking the prescription drugs sulfasalazine or hydroxychloroquine. Large, high-quality studies in humans are needed comparing effects of cat's claw vs. placebo before a conclusion can be drawn.
Knee pain caused by osteoarthritis
Early research suggests that cat's claw may reduce pain from knee osteoarthritis. Further research is needed to confirm these results.
Several low-quality studies suggest that cat's claw may slow tumor growth. However, this research is very early and has not identified specific types of cancer that may benefit; the results are not clear. More studies are needed before a recommendation can be made.
A few early studies suggest that cat's claw may boost the immune system, including in patients with HIV. However, results from different studies have not agreed with each other. Therefore, there is not enough information to recommend cat's claw for this use.
Cat's claw has been suggested for many other uses, based on tradition or on scientific theories. However, these uses have not been thoroughly studied in humans, and there is limited scientific evidence about safety or effectiveness. Some of these suggested uses are for conditions that are potentially very serious and even life-threatening. You should consult a health care professional before using cat's claw for any unproven use.
Chronic fatigue syndrome
Drug or radiation side effects
Enhanced DNA repair
High blood pressure
Multidrug resistance of tumor cells
Ozone-induced lung inflammation
Recovery from childbirth
Sexually transmitted diseases
Urinary tract infection or inflammation
People with allergies to plants in the Rubiaceae family or any species of Uncaria may be more likely to have allergic reactions to cat's claw. A typical allergic reaction may be itching or severe rash. Allergic inflammation of the kidneys has been reported.
Few side effects have been reported from using cat's claw at recommended doses. Most side effects are believed to be rare, and some side effects are theoretical and have not been reported in humans. Examples of possible side effects include stomach discomfort, nausea, diarrhea, slow heartbeats or altered rhythm of heartbeats, kidney disease, acute kidney failure, neuropathy, decreases in estrogen or progesterone levels and an increased risk of bleeding. Because cat's claw theoretically may increase the risk of bleeding, you may need to stop taking cat's claw before some surgeries; discuss this with your health care professional.
Some natural medicine experts discourage the use of cat's claw in people with conditions affecting the immune system, such as AIDS or HIV, some types of cancer, multiple sclerosis, tuberculosis and rheumatologic diseases (rheumatoid arthritis, lupus, etc.). However, there are no specific studies or reports in this area, and the risks of cat's claw use in people with these conditions are not clear.
Be aware that many tinctures contain high levels of alcohol and should be avoided when driving or operating heavy machinery.
Pregnancy And Breast-Feeding
Cat's claw cannot be recommended during pregnancy or breast-feeding. Historically, cat's claw has been used to prevent pregnancy and to induce abortion. Women who are pregnant or wish to become pregnant should not take cat's claw. Also, be aware that many tinctures contain high levels of alcohol and should be avoided during pregnancy.
Interactions with drugs, supplements and other herbs have not been thoroughly studied. The interactions listed below have been reported in scientific publications. If you are taking prescription drugs, speak with a health care professional or pharmacist before using herbs or dietary supplements.
Interactions With Drugs
In theory, cat's claw may increase the risk of bleeding when used with anticoagulants (blood thinners) or antiplatelet drugs. Examples include warfarin (Coumadin), heparin and clopidogrel (Plavix). Some pain relievers may also increase the risk of bleeding if used with cat's claw. Examples include aspirin, ibuprofen (Motrin, Advil) and naproxen (Naprosyn, Aleve, Anaprox). There is evidence that cat's claw may interfere with the way the liver breaks down certain drugs. As a result, cat's claw may cause the levels of drugs in the body to be too high, leading to serious side effects. If you are taking prescription drugs, ask a health care professional or pharmacist for advice before you take cat's claw.
Because one component in cat's claw may alter the rhythm of the heart (for example, it may slow heartbeats) or lower blood pressure, cat's claw should be used cautiously by people who take drugs to treat irregular heart rhythms, such as amiodarone (Cordarone) or digoxin (Lanoxin), or drugs to lower blood pressure, such as verapamil (Calan). Because cat's claw is believed to affect the immune system, people taking immunosuppressants such as corticosteroids, drugs for rheumatologic diseases (rheumatoid arthritis, lupus, etc.) or drugs to prevent rejection of transplanted organs should consult a health care professional or pharmacist before using cat's claw. Examples of such drugs are azathioprine, cyclosporine and prednisone.
Be aware that many tinctures contain high levels of alcohol and may cause nausea or vomiting when taken with metronidazole (Flagyl) or disulfiram (Antabuse). Drugs that act on muscarinic or seratonergic receptors may be affected.
Interactions With Herbs And Dietary Supplements
Very few interactions between cat's claw and herbs or supplements have been reported. In theory, cat's claw may increase the blood levels of herbs broken down by the liver, such as chasteberry (Vitex agnus-castus). Check with a health care professional before starting cat's claw if you are taking other herbs or supplements. It is possible that cat's claw may lower blood pressure or alter the rhythm of heartbeats. As a result, cat's claw should be used carefully if also taken with other herbs that affect the heart, such as foxglove.
In theory, cat's claw may increase the risk of bleeding when also taken with other products that are believed to increase the risk of bleeding. Examples include Ginkgo biloba
Cat's claw may decrease the effectiveness of iron supplements. Herbs and supplements that act on muscarinic or seratonergic receptors may be affected.
The doses listed below are based on scientific research, publications or traditional use. Because most herbs and supplements have not been thoroughly studied or monitored, safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients even within the same brand. Combination products often contain small amounts of each ingredient and may not be effective. Appropriate dosing should be discussed with a health care professional before starting therapy; always read the recommendations on a product's label. The dosing for unproven uses should be approached cautiously, because scientific information is limited in these areas.
Some recommendations for the standardization of cat's claw have been made by natural medicine experts. One suggestion is that products be standardized to contain 3 percent alkaloids and 15 percent phenols per dose. Another recommendation is for cat's claw products to contain 1.3 percent pentacyclic oxindole alkaloids. Doses of 250 and 350 millgrams per day have been studied for antioxidant effects.
Adults (Aged 18 Or Older)
Capsules: A dose of 250 to 1,000 milligrams once to three times daily taken by mouth has been used.
Extract: An extract containing only pentacyclic oxindole alkaloids in 20 milligrams two or three times daily for the first 10 days and then 20 milligrams afterwards taken by mouth has been used.
Tincture: A dose of one to two milliliters two to three times daily or 20 to 40 drops five times daily taken by mouth has been used.
Decoction: A dose of one tablespoon of pulverized root in one quart of hot water taken before breakfast by mouth has been used.
Tea: A dose of one to 25 grams of root bark has been added to 250 milliliters of water, boiled for five to 10 minutes, then cooled and strained. One cup taken three times daily by mouth has been used.
Cat's claw is also available in preparations for the skin, but no specific doses have been shown to be safe or effective.
Children (Younger Than 18)
The dosing and safety of cat's claw have not been studied thoroughly in children, and it is recommended that you discuss doses with a health care professional before your child starts therapy. Some natural medicine practitioners recommend children aged 3 to 6 years may take 20 milliliters of tea in 20 milliliters of hot water in the morning by mouth. However, there is no scientific support or safety data for this formula.
Although cat's claw has been suggested for many conditions, more studies are needed before it can be recommended as a treatment for any health condition. It should be avoided in pregnant or breast-feeding women and used only in children if recommended by a health care professional. Remember that tinctures can contain large amounts of alcohol and may cause nausea or vomiting if taken with the drugs disulfiram or metronidazole. Use cat's claw with caution if you are prone to bleeding disorders or if you are taking drugs that increase the risk of bleeding. Consult a health care professional immediately if you experience side effects.
The information in this monograph was prepared by the professional staff at Natural Standard, based on thorough systematic review of scientific evidence. The material was reviewed by the Faculty of the Harvard Medical School with final editing approved by Natural Standard.
- Natural Standard: An organization that produces scientifically based reviews of complementary and alternative medicine (CAM) topics
- National Center for Complementary and Alternative Medicine (NCCAM): A division of the U.S. Department of Health & Human Services dedicated to research
Selected Scientific Studies: Cat's Claw
Natural Standard reviewed more than 125 articles to prepare the professional monograph from which this version was created.
Some of the more recent studies are listed below:
- Castaneda O, Leon G, Leon D, et al. Cat's claw vs. placebo in rheumatoid arthritis. Paper presented at Symposium on Uncarias, Lima, Peru, 1997.
- Kitajima M, Hashimoto K, Yokoya M, et al. Two new nor-triterpene glycosides from peruvian "Una de Gato" (Uncaria tomentosa). J Nat Prod 2003;66(2):320-323.
- Mur E, Hartig F, Eibl G, Schirmer M. Randomized double blind trial of an extract from the pentacyclic alkaloid-chemotype of uncaria tomentosa for the treatment of rheumatoid arthritis. J Rheumatol 2002;Apr, 29(4):678-681.
- Piscoya J, Rodriguez Z, Bustamante SA, et al. Efficacy and safety of freeze-dried cat's claw in osteoarthritis of the knee: mechanisms of action of the species Uncaria guianensis. Inflamm Res 2001;50(9):442-448.
- Silva H, Diaz R, Segami I. Double blind clinical test comparing Uncaria guianesis against placebo in single daily dosage to treat knee osteoarthritis. Paper presented at Symposium on Uncarias, Lima, Peru, 1997.
- Watanabe H, Zhao Q, Matsumoto K, et al. Pharmacological evidence for antidementia effect of Choto-san (Gouteng-san), a traditional Kampo medicine. Pharmacol Biochem Behav 2003;75(3):635-643.
Last updated July 14, 2005
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