Harpagophytum procumbens and a closely related plant, Harpagophytum zeyheri, are native to southern Africa and Madagascar. They are the only two species in Harpagophytum, a genus in the sesame family. Both species have comparable anti-inflammatory and pain-reducing activity, and both are used as a source of Harpagophyti radix.

According to traditional folklore, the Khoisan of the Kalahari used the dried root in remedies to treat pain, pregnancy complications, and skin disorders. Devil's claw has appetite stimulating and mildly analgesic pharmacological actions. Today, this bitter-tasting plant is sold in Europe and Canada as a digestive aid and appetite stimulant.

Devil's claw is collected from the savannas and outskirts of the Kalahari Desert in South Africa and Namibia. The drug is made from dried, secondary tubers. The root tubers are always sliced or pulverized before they are dried because they are nearly impossible to cut once they have dried.

Devil's claw is a leafy perennial with a branched root system and branched shoots. The fruit consists of large woody grapples that are pointed and barbed. The secondary tuber roots grow out of the main and lateral roots. The root tubers (also called peripheral tubers) can reach a size of 20 cm long and 3 cm thick. The crude drug is made from the dried, yellowish-gray to bright pink tubers.

• Roots (rhizome)
• Dried secondary tubers

Monoterpenes include mainly harpagoside (0.5% to 1.6%; extremely bitter iridoid glycoside), harpagide, procumbide; phenylethanol derivatives include acteoside (verbascoside), isoaceteoside; oligosaccharides; harpagoquinones; other compounds (carbohydrates, amino acids, flavonoids).

Dried powder capsules and fluid extract preparations are made from dried secondary tubers.

Traditional herbal actions: antirheumatic, analgesic, sedative, diuretic, antipyretic, anti-inflammatory; Newall painful arthroses, tendinitis, dyspepsia, liver and gallbladder problems, loss of appetite (anorexia); supportive treatment for degenerative musculoskelatal conditions (disorders of locomotive system)

Clinical applications: Rheumatic and joint disorders such as rheumatoid arthritis, osteoarthritis, and gout. Conditions involving inflammation of connective tissues such as fibromyalgia, fibrositis, tendinitis, adhesions due to scar tissue. Liver, kidney, and bladder disorders; allergies; arteriosclerosis; lumbago; gastrointestinal problems; menstrual symptoms; neuralgia; headache; heartburn; nicotine poisoning

Several in vitro and in vivo investigations confirm that aqueous extracts of devil's claw and its primary active principle, harpagoside, have anti-inflammatory and anti-exudative effects. In one study, devil's claw exhibited anti-inflammatory effects comparable to those of the antiarthritic drug, phenylbutazone. Anti-inflammatory effects have been strongest in semi-chronic rather than in acute inflammatory animal models. In another investigation, however, devil's claw failed to show anti-inflammatory properties when compared to aspirin and indomethacin. Other studies have not unequivocally shown that devil's claw reduces inflammation in either animals or humans. Inconsistent findings on efficacy may be due to different modes of administering the drug. Gastric juices apparently inactivate some of the active constituents. Therapeutic effects may be difficult to demonstrate in animal models unless devil's root extracts are protected from gastric enzymes.

In an in vitro experiment, indomethacin and aspirin caused a 5% inhibition of prostaglandin synthetase activity, but devil's claw did not produce a significant reduction in enzyme activity. In vitro research also shows that harpagoside diminished the contractile response of smooth muscle in isolated muscle preparations. Harpagoside and other active principles presumably are able to alter the contractile response by disrupting calcium influx. In addition, devil's claw extracts have weak antifungal properties.

Devil's claw extracts are cardioactive and have protective activity against ventricular arrhythmias. However, the cardioactive effects are not entirely due to harpagoside. Instead, cardioprotecive properties are attributed to a synergy between hapagoside and other active constituents in the crude extract.

The biochemical action of devil's claw on arachidonic acid metabolism apparently differs from the mechanisms of action found in NSAIDs. The therapeutic effects are perhaps explained by in vivo conversion (via enzymatic hydrolysis) of either harpagoside or harpagide into harpagogenin.

In a double-blind, placebo-controlled clinical study, 89 patients with rheumatoid symptoms were given 2 g of powdered devil's claw daily for two months. The treatment group had significant improvements compared to the placebo group in sensitivity to pain and in flexibility measured by fingertip-floor distance.

• Dried tuber: Take 0.1 to 0.25 g tid, encapsulated or as decoction.
• Fluid extract (1:1 in 25% alcohol): Take 0.1 to 0.25 ml tid.
• Tincture (1:5 in 25% alcohol): Take 0.5 to 1.0 ml tid.

Most experts consider devil's claw nontoxic and safe.

No side effects have been reported for devil's claw root when it is administered in recommended therapeutic doses. However, this herb should not be used in excess because information on toxicology is limited. Cardioactivity makes it potentially risky for individuals with certain medical conditions because devil's claw stimulates gastric secretions. Individuals with gastric and/or duodenal ulcers, and/or gallstones should not take devil's claw without the advice of a physician or other qualified health care provider. Cinnamylic acid and terpene in devil's claw may trigger allergic effects. Despite a common misconception that devil's claw is an abortifacient, pharmacological research suggests that this plant does not induce abortion. However, digestive stimulants such as devil's claw should not be used in pregnancy because of the reflexive action on uterine muscle.

Devil's claw and warfarin may interact, resulting in purpurea (Shaw et al. 1991). The mechanism for this interaction is unclear and there is no data available regarding effects from rechallenge. Patients taking devil's claw with anticoagulants should be monitored closely for clinical signs of over-coagulation or bleeding disorders.

The U.S. FDA classifies devil's claw as a dietary supplement. The plant is accepted in France for specified indications. It is approved by the German Commision E. Devil's claw is not included on the General Sale List in Britain.

Baghdikian B, Lanhers M, Fleurentin J, et al. An analytical study, anti-inflammatory and analgesic effects of Harpagophytum procumbens and Harpagophytum zeyheri. Planta Med. 1997;63:171-176.

Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, Mass: Integrative Medicine Communications; 1998.

Bradley P, ed. British Herbal Compendium. Dorset, England: British Herbal Medicine Association; 1992;1:96-98.

British Herbal Pharmacopoeia. 4th ed. Dorset, England: British Herbal Medicine Association; 1996.

Costa de Pasquale R, Busa G, Circosta C, et al. A drug used in traditional medicine: Harpagophytum procumbens DC. III. Effects on hyperkinetic ventricular arrhythmias by reperfusion. J Ethnopharmacology. 1985;13:193-9.

Grahame R, Robinson B. Devil's claw (Harpagophytum procumbens): pharmacological and clinical studies. Ann Rheum Dis. 1981;40:632.

Guyader M. 1984. Les plantes antirhumatismales. Etude historique et pharmacologique, et etude clinique du nebulisat d'Harpagophytum procumbens DC chez 50 patients arthrosiques sivis en service hospitalier. Paris: Universite Pierre et Marie Curie.

Lanhers MC, Fleurentin J, Mortier F, Vinche A, Younos C. Anti-inflammatory and analgesic effects of an aqueous extract of Harpagophytum procumbens. Planta Med. 1992;58:117-123.

Mabberley DJ. The Plant-Book: A Portable Dictionary of the Higher Plants. Cambridge, England: Cambridge University Press; 1987.

McLeod D, et al. Investigations of Harpagophytum procumbens (Devil's Claw) in the treatment of experimental inflammation and arthritis in the rat. Br J Pharmacol. 1979;66:140P.

Moussard C, Alber D, Toubin M, Thevenon N, Henry JC. A drug used in traditional medicine, Harpagophytum procumbens: no evidence for NSAID-like effect on whole blood eicosanoid production in human. Prostaglandins Leukot Essent Fatty Acids. 1992;46:283-286.

Newall C, Anderson L, Phillipson J. Herbal Medicines: A Guide for Health-care Professionals. London: Pharmaceutical Press; 1996.

Occhiuto F, Circosta C, Ragusa S, Ficarra P, Costa De Pasquale R. A drug used in traditional medicine: Harpagophytum procumbens DC. IV. Effects on some isolated muscle preparations. J Ethnopharmacol. 1985;13:201-208.

Schulz V, Hänsel R, Tyler VE. Rational Phytotherapy: A Physicians' Guide to Herbal Medicine. 3rd ed. Berlin: Springer-Verlag; 1998.

Shaw D, Leon C, Kolev S, Murray V. Traditional remedies and food supplements: A 5-year toxicological study (1991-1995). Drug Safety. 1991;17(5):342-356.

Tyler VE. The Honest Herbal: A Sensible Guide to the Use of Herbs and Related Remedies. 3rd ed. Binghamton, NY: Pharmaceutical Products Press; 1993.

Whitehouse L, et al. Devil's Claw (Harpagophytum procumbens): no evidence for anti-inflammatory activity in the treatment of arthritic disease. Can Med Assoc J. 1983;129:249-251.