Natural Products

Devil's Claw

Harpagophytum procumbens

Efficacy

• Indications with proven efficacy:
  None
• Indications with possible, but poorly documented efficacy - the use of this product cannot be recommended:
  Indigestion
  Loss of appetite
  Osteoarthritis and musculoskeletal pain
  
• Also used for these other indications, but with no proof of efficacy:
  Arteriosclerosis
  Bladder and kidney problems
  Gout
  Menstrual problems
  Myalgia
  Rheumatoid arthritis
  Wounds (topically)

Security

• Risk of Drug Interactions: Low
• Adverse Effects: Not Frequent

What is it?

Devil's claw is a plant known under the scientific name of Harpagophytum procumbens. Only its roots are used, since other parts of the plants appear to be of no interest. Researchers are uncertain about which constituent(s) might be responsible for its activity. Harpagoside and its derivatives have shown inconsistent activity.

The name of the plant comes from the appearance of the fruit, which is covered by hooks meant to attach to the fur of passing animals thus spreading the seeds in the environment.

Devil's claw root is usually standardized to 3% iridoid glycosides or 2% harpagoside.

Warning

In 2004, Canada adopted new regulations that control the manufacturing, packaging, labeling and importing of natural health products. The new regulations also include an adverse reaction reporting system. Products that conform to the regulation's criteria are identified with a natural product number (NPN) or homeopathic medicine number (DIN-HM) and can be legally sold in Canada. This number indicates that the product meets specific criteria for safety and purity, not that it is effective for any indication.

Medicinal plants content varies naturally from plant to plant – just as fruits from the same package may vary in taste and texture. There is no standard to measure the active content of each plant. Thus, efficacy of natural products should be expected to vary from brand to brand as well as from bottle to bottle of the same brand.

For more information about the Natural Health Products Regulations, or to check if a product has been assessed, visit the Health Canada website at http://www.hc-sc.gc.ca/dhp-mps/prodnatur/index-eng.php.

Does it work?

There is no evidence that devil's claw is effective in any indication. However, it is used to treat certain medical conditions where it may be of some benefits:

• Indigestion:
  Devil's claw may increase bile volume, which could improve the digestion of lipids. A typical dose is 500 mg of root 3 times a day.
• Rheumatic disorders, adjunct:
  Devil's claw appear to have a mild effect against pain, which is most probably insufficient to relieve severe pain, but could be useful as an adjunct to other therapies. Doses used are 1.5 to 3 grams of root per day.
• Loss of appetite:
  Devil's claw seems to slightly increase appetite when 500 mg of root is administered 3 times a day. For this indication, decoction or liquid extract would be more effective and enteric-coated tablets should be avoid.

There is insufficient reliable information to conclude that devil's claw is effective in any other indications, including topical application as an analgesic. A well-designed study would have showed that devil's claw is not effective against arthritis.

Is it safe?

• Devil's claw does not appear to be associated with any severe toxicity. The most common adverse effects are diarrhea, nausea, vomiting and abdominal pain. In one study, an arthritic patient reported severe headaches, buzzing in the ears, marked loss of appetite and loss of taste. No other study participants reported adverse effects. The safety of long-term use remains undetermined.
• Devil's claw is contraindicated in patients with gastric and duodenal ulcers. It should be used with great caution in individuals with suspected gallstones (biliary lithiasis).
• Because the product may cause uterine contractions, it is contraindicated during pregnancy. Since there is no safety data available concerning its use during breast-feeding, lactating women should not use devil's claw.

Clinical Notes

• Devil's claw is usually used to treat arthritis and other such diseases. However, scientific information currently available has failed to prove its efficacy. Because its long-term safety is still undetermined, one cannot recommend the long-term use warranted by such chronic disorders.

References

1. Blumethal M et al. The Complete German Commission E monographs, 1998
2. Natural Medicines Comprehensive Database, Therapeutic Research Faculty, 2007
3. Lininger S. et Al. The Natural Pharmacy, Prima Health, 1998
4. Barnes J. et Al. Herbal Medicines, 2e Edition, Pharmaceutical Press, 2002
5. Pierce Andrea, Practical Guide to Natural Medicines, 1999
6. Passeportsanté.net. Griffe du diable. http://www.passeportsante.net
7. Rotblatt M. and Ziment I. Evidence-Based Herbal Medicine, Hanley & Belfus, 2002