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Cat's Claw

Scientific Name(s): Uncaria guianensis (Aubl.) Gmel., Uncaria tomentosa (Willd.) DC
Common Name(s): C-Med 100, Cat's claw, Cortex Uncariae, Life-giving vine of Peru, Reparagen, Samento, Uña de gato
Drug class: Herbal products

Medically reviewed by Last updated on Sep 6, 2021.

Clinical Overview


Despite multiple purported effects, controlled clinical trials are lacking.


One gram of root bark given 2 to 3 times daily is a typical dose, while 20 to 30 mg of a root bark extract has been recommended. Clinical trials are generally lacking to support appropriate dosages. A standardized extract containing 8% to 10% carboxy alkyl esters and less than 0.5% oxindole alkaloids has been used in clinical studies in doses of 250 to 300 mg.


Cat's claw products should be avoided before and after surgery, as well as by those using immunosuppressant therapy and in children due to lack of safety data.


Information regarding safety and efficacy during pregnancy and lactation is lacking.


See Drug Interactions section.

Adverse Reactions

Although reports of adverse effects are rare, GI complaints (nausea, diarrhea, stomach discomfort), renal effects, neuropathy, and an increased risk of bleeding with anticoagulant therapy are possible.


Historical ethnomedicinal evidence and current use by consumers suggest low toxicity; however, toxicological studies are limited.

Scientific Family

  • Rubiaceae


Cat's claw is a tropical vine of the madder family (Rubiaceae). The name describes the small, curved-back spines on the stem at the leaf juncture. The genus Uncaria is found mainly in tropical regions of Southeast Asia, the Asian continent, and South America. There are 34 reported species of Uncaria.

U. tomentosa and U. guianensis species are found in South America and are lianas, or high-climbing, twining, woody vines growing up to 305 m in length and several centimeters in diameter. Both species are known in Peru as uña de gato (Spanish for cat's claw). Large amounts of U. guianensis are collected in South America for the European market, while American sources prefer U. tomentosa. By 1997, over 50 dietary supplement manufacturers offered cat's claw products in the United States.

One Asian species, known as gambir or pole catechu (Uncaria gambir [Hunter] Roxb.), is a widely used tanning agent that also has had a long history of medicinal use as an astringent and antidiarrheal. The related species Uncaria rhynchophylla is more commonly used in China.PLANTS 2011, WHO 2007, Heitzman 2005


Cat's claw has had a history of folkloric use in South America for wound healing and for treating arthritis, gastric ulcers, intestinal disorders, and some skin disorders and tumors. The part used medicinally is the inner bark of the vine or root. In Peru, a boiled decoction of U. guianensis is used as an anti-inflammatory, antirheumatic, and contraceptive agent, as well as for treating gastric ulcers and tumors, gonorrhea (by the Bora tribe), dysentery (by the Indian populations of Colombia and Guiana), and cancers of the urinary tract in women. The Ashanica Indians believe that samento (U. tomentosa) has life-giving properties and ingest a cup of the decoction every 1 to 2 weeks to ward off disease, treat bone pain, and cleanse the kidneys. Other reported uses include treatment for abscesses, asthma, chemotherapy adverse effects, fever, hemorrhage, rheumatism, skin impurities, urinary tract inflammation, weakness, and wounds, as well as for disease prevention and recovery from childbirth.

Demand for the bark has been partially attributed to European reports of its clinical use with zidovudine in AIDS treatment. The demand for the bark in the United States is based on its purported use as a tea in treating diverticulitis, hemorrhoids, peptic ulcers, colitis, gastritis, parasites, and "leaky gut syndrome." There are, however, no controlled clinical trials to support these uses.WHO 2007, Keplinger 1999, Duke 1994


Many reports exist on the chemical composition of the various Uncaria species and differentiations of the compounds found in different plant parts; reviews have also been published. More than 150 chemical compounds have been isolated from the genus, with approximately 50 chemical entities attributed to U. tomentosa, some of which possibly novel to that species.

Two different chemotypes of U. tomentosa have been described, while U. guianensis and U. rhynchophylla have also been extensively studied. No official standardization exists, and commercially available preparations may consist of mixed plant sources despite claiming to be "100% pure." Inter-batch variations have been reported.

Key compounds common to the genus are primarily the indole and oxindole alkaloids, pentacyclic triterpenoids, and flavonoids. Alkaloids found in most of the species include hirsuteine, hirsutine, mitraphylline, and rhychophylline. The terpenoids include cytotoxic phenolic acid esters, uncarric acids, and glycosides, while other novel compounds include quinovic acids, sterols, and coumarins.Heitzman 2005, Kitajima 2003, Laus 2004, Erowele 2009, Hemingway 1974

Uses and Pharmacology


Cat's claw is a potent inhibitor of production of the pro-inflammatory cytokine tumor necrosis factor (TNF)-alpha in vitro. The anti-inflammatory activity appears to involve suppression of TNF-alpha synthesis, as well as the secretion of nitric oxide and interleukins.Sandoval 2009, Zeng 2009, Kim 2010, Allen-Hall 2010 The antioxidant activity associated with the phenolic and flavonoid content does not appear to be related to inhibition of nuclear factor kappaB (NF-kB) because quinic acid esters have no inherent antioxidant potential, but inhibit NF-kB.Zeng 2009, Amaral 2009

Animal data

The pentacyclic oxindole alkaloids were possibly associated with the anti-inflammatory activity of 2 extracts from U. tomentosa when tested in mouse paw edemaAguilar 2002; however, CNS pathways such as serotonin receptors may also be involved.Jürgensen 2005 Induced lung inflammation was reduced in mice pretreated with U. tomentosa bark extract.Cisneros 2005

Clinical data

Limited clinical studies suggest an anti-inflammatory action of cat's claw in osteoarthritis.Hardin 2007, Mehta 2007 A small trial (N = 45) found improved subjective measures of pain with cat's claw; however, other objective measures were not significantly altered. Adverse effects were comparable with placebo.Piscoya 2001 In another small randomized trial (N = 40), U. tomentosa extract resulted in a reduction in the number of painful joints in patients with rheumatoid arthritis compared with placebo.Mur 2002 A 2010 systematic review identified 4 randomized controlled trials that studied cat’s claw for osteo- or rheumatoid arthritis; 2 of the trials used the herb in combination with other herbs. Of the 2 using only cat’s claw, one is cited above and the second additional randomized clinical trial was a double-blind trial conducted in 45 men with osteoarthritis of the knee. Administration of 100 mg cat’s claw extract for 4 weeks led to significant improvements in pain with activity as well as both patient- and physician-assessed pain scores compared to placebo (P<0.001).Rosenbaum 2010

Antimicrobial activity

Alkaloidal extracts of U. tomentosa have shown in vitro antiviral activity against the vesicular stomatitis virus, rhinovirus, and Dengue virus.Aquino 1989, Reis 2008 Antibacterial activity has been demonstrated in vitro to human oral pathogens, such as S. mutans and S. aureus, but not C. albicans or P. aeruginosa.Ccahuana-Vasquez 2007 Clinical studies are lacking.


Experimental studies have shown antiproliferative (antimitotic) and apoptotic activity of extracts of U. tomentosa. Cell lines evaluated include human leukemicAnter 2011, Pilarski 2007; lymphomaHeitzman 2005, Laus 2004; lung, cervical, and colon carcinomaPilarski 2010; as well as neuroblastoma and glioma.García Prado 2007 A protective effect was demonstrated in vitro against ultraviolet damage of skin cells.Mammone 2006 Different preparations of U. tomentosa contain different alkaloids and result in varying cellular responses that may be related to antioxidant action on signaling pathways.Heitzman 2005, Laus 2004, Anter 2011, Mammone 2006, Gurrola-Díaz 2011 Extracts of U. guianensis and U. rhynchophylla containing uncarine triterpenes have also been evaluated for their cytotoxic effects.Laus 2004, Bae 2010

Animal data

Studies in animal rodent models have shown a reduction in tumor growth with use of extracts of U. tomentosa.Pilarski 2010

Clinical data

Clinical studies are limited. One ex vivo study using human leukemic cells obtained from children demonstrated an increased survival when exposed to extracts of U. tomentosa; therefore, caution is advised.Styczynski 2006 One phase 2 prospective open-label study investigated the safety and efficacy of dry root bark extract of U. tomentosa on adults with advanced solid tumors and no alternative therapeutic options. After 8 weeks of 100 mg 3 times daily, the average overall quality of life, social functioning, and fatigue improved significantly (P=0.041, P=0.034, and P=0.049, respectively); however, no tumor response to the medication was Paula 2015

Cardiovascular effects

Older data from in vitro and animal studies suggested hypotensive, diuretic, and vasorelaxant activity of rhynchophylline, mytraphylline, and gambirine.Hemingway 1974, Harada 1979, Harada 1976, Mok 1992 However, clinical studies are lacking.

CNS effects

Although the mechanism of action remains unclear, pteropodine and isopteropodine may increase the affinity of agonists or act as positive modulators of muscarinic M1 and 5-HT2 receptors, improving impaired cognitive processes.Kang 2002 In vitro binding of mitraphylline to amyloid proteinFrackowiak 2006 and an apparent improvement in functioning in amyloid precursor protein transgenic mice by Yokukansan (a combination preparation containing Uncaria hook)Fujiwara 2011 suggest investigative potential as Alzheimer disease therapeutic agents. Yokukansan and U. rynchophylla have been evaluated for other CNS effects, including Caires 2010, Tang 2010, Lo 2010, Kawakami 2011

Estrogen effects

Studies are conflicting on the effect of U. tomentosa extracts on estrogen receptors.Budán 2011 In rats with induced endometriosis, cat's claw preparations decreased the volume of foci and exerted possible anti-inflammatory and immune-modulatory activity.Nogueira Neto 2011


All individual alkaloids of U. tomentosa, with the exception of rhynchophylline and mitraphylline, have immunostimulant propertiesWagner 1985 and the ability to enhance phagocytosis in vitro. Researchers have shown that pteropodine and isopteropodine have immune-stimulating effects.Jones 1994 Controlled clinical trials are lacking; however, an uncontrolled study suggested a positive effect on lymphocytes in HIV-positive individuals.Erowele 2009


One gram of root bark given 2 to 3 times daily is a typical dose, while 20 to 30 mg of a root bark extract has been recommended.WHO 2007 Clinical trials are generally lacking to support appropriate dosages. A standardized extract based on a particular chemotype of this species containing 8% to 10% carboxy alkyl esters and less than 0.5% oxindole alkaloids has been used in clinical studies in doses of 250 to 300 mg.Lehmann-Willenbrock 1988, Sheng 2001

Pregnancy / Lactation

Information regarding safety and efficacy during pregnancy and lactation is lacking. U. tomentosa has traditionally been used as an emmenagogue.WHO 2007, Erowele 2009


Agents with antihypertensive properties: Herbs (antihypertensive properties) may enhance the adverse/toxic effect of agents with antihypertensive properties. Consider therapy modification.Ernst 2003

Agents with antiplatelet properties: Herbs (anticoagulant/antiplatelet properties) may enhance the adverse/toxic effect of agents with antiplatelet properties. Bleeding may occur. Consider therapy modification.Ernst 2003, Mousa 2010, Stanger 2012, Spolarich 2007, Ulbricht 2008

Anticoagulants: Herbs (anticoagulant/antiplatelet properties) may enhance the adverse/toxic effect of anticoagulants. Bleeding may occur. Consider therapy modification.Ernst 2003, Mousa 2010, Stanger 2012, Spolarich 2007, Ulbricht 2008

Herbs (anticoagulant/antiplatelet properties): May enhance the adverse/toxic effect of other herbs (anticoagulant/antiplatelet properties). Bleeding may occur. Consider therapy modification.Ernst 2003, Mousa 2010, Stanger 2012, Spolarich 2007, Ulbricht 2008

Nonsteroidal anti-inflammatory agents: Herbs (anticoagulant/antiplatelet properties) may enhance the adverse/toxic effect of nonsteroidal anti-inflammatory agents. Bleeding may occur. Consider therapy modification.Ernst 2003, Mousa 2010, Stanger 2012, Spolarich 2007, Ulbricht 2008

Salicylates: Herbs (anticoagulant/antiplatelet properties) may enhance the adverse/toxic effect of salicylates. Bleeding may occur. Consider therapy modification.Ernst 2003, Spolarich 2007, Ulbricht 2008

Thrombolytic agents: Herbs (anticoagulant/antiplatelet properties) may enhance the adverse/toxic effect of thrombolytic agents. Bleeding may occur. Consider therapy modification.Ernst 2003, Mousa 2010, Stanger 2012, Spolarich 2007, Ulbricht 2008

Protease inhibitors/herbs: Plasma concentrations and pharmacologic effects of atazanavir, ritonavir oral, and saquinavir mesylate oral may be increased by cat's claw (Uncaria tomentosa) oral. A case report of significantly elevated trough levels of protease inhibitors without signs or symptoms of toxicity was reported after recent initiation of cat’s claw supplement that resolved upon discontinuation of supplement use. Trough levels of atazanavir, ritonavir, and saquinavir fell to normal levels from 1.22 to 0.3, 6.13 to 0.92, and 3.4 to 0.64 microg/mL, respectively, within 15 days of cat’s claw discontinuation.Lopez Galera 2008 The likelihood of this being a result of a lab interaction or a pharmacological interaction was not addressed.

Adverse Reactions

Case reports of adverse events are rare, although information is lacking. The American Herbal Products Association rates Uncaria preparations as class 4 (lack of data to support safety).Erowele 2009, Piscoya 2001

Possible adverse effects include GI complaints (nausea, diarrhea, stomach discomfort), renal effects (a case report of acute renal failure exists), hormonal effects (in vitro data suggest extracts may interact with estrogen-receptor binding sites), neuropathy (a case report of worsened Parkinson disease symptoms exists),Cosentino 2008 and an increased risk of bleeding with anticoagulant therapy.Cosentino 2008, Ernst 2003, Erowele 2009, Vogel 2005 A case of silicate nephrolithiasis was reported in a 38-year-old woman with a history of Lyme disease, osteoarthritis, gallstones, and irritable bowel syndrome who had been taking several dietary supplements for a few years. Three of the supplements contained silica dioxide as an ingredient, one of which was cat’s claw. Her symptoms of flank pain and gravel-like urine sediment resolved upon discontinuation of her supplements and recurred upon restarting them.Flythe 2009

It is recommended that Uncaria-containing products be avoided before and after surgery, by those using immunosuppressant therapy, and in children due to lack of safety data.Erowele 2009

Data collected between 2004 and 2013 among 8 US centers in the Drug-induced Liver Injury Network revealed 15.5% (130) of hepatotoxicity cases was caused by herbals and dietary supplements whereas 85% (709) were related to medications. Of the 130 related cases of liver injury related to supplements, 65% were from non-bodybuilding supplements and occurred most often in Hispanic/Latinos compared to non-Hispanic whites and non-Hispanic blacks. Liver transplant was also more frequent with toxicity from non-bodybuilding supplements (13%) than with conventional medications (3%) (P<0.001). Overall, the number of severe liver injury cases was significantly higher from supplements than conventional medications (P=0.02). Of the 217 supplement products implicated in liver injury, cat's claw was among the 22% (116) of the single-ingredient products.Navarro 2014


Historical ethnomedicinal evidence and current use by consumers suggest low toxicity; however, toxicological studies are limited. In rats, the median lethal dose of a single dose of a water extract of U. tomentosa was determined to be greater than 8 g/kg. In humans, there were no toxic adverse effects observed at a repeated dose of 350 mg/day for 6 consecutive weeks.WHO 2007, Williams 2001, Sheng 2000, Valerio 2005

Index Terms

  • Uncaria rhynchophylla


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