Devil's Claw

The medicinal preparations of devil's claw are made from the dried roots of Harpagophytum procumbens, a South African plant. Other common names include grapple plant, and wood or wool spider plant. The fruits have long, branching arms with "claw­like" hooks.

Uses and Benefits:

Since it's introduction to Europe from Africa in the early 20th century, devil's claw has been used most frequently as an analgesic and anti-inflammatory agent for arthritis and other painful musculoskeletal conditions. It has also been used for anorexia and dyspepsia, as a bitter tonic, and as an antipyretic. Topical applications include wounds, ulcers, and pain relief.

Pharmacology:

The main active constituent is harpagoside, an iridoid glucoside thought to have anti-inflammatory activity; however, it does not adequately account for all of the herb's anti­inflammatory effects. The anti-inflammatory mechanism of devil's claw appears to be different from that of aspirin or NSAIDs. In vitro, devil's claw does not affect prostaglandin synthetase activity. In humans, administration of 2 g of powdered devil's claw produced no effect on eicosanoid biosynthesis, either by the cyclo-oxygenase or the 5-lipoxygenase pathways.In animal models, devil's claw extracts demonstrated inconsistent anti-inflammatory activity in experimentally induced inflammation. Extracts administered parenterally were more effective than oral administration, and aqueous extracts consistently demonstrated more anti-inflammatory activity than alcohol extracts or isolated constituents.

Concern about degradation of active constituents by gastric acid supports the use of enteric coated preparations.

Devil's claw extracts have anti-arrhythmic activity in animal models, but this effect has not been tested in humans.

Clinical Trials:

The effectiveness of devil's claw has been evaluated in a number of controlled clinical trials for osteoarthritis, low back pain, and other rheumatic and musculoskeletal complaints. Several studies are not available in English, and are thus summa­rized from other sources. Dosage and preparations varied in the clinical trials, but treatment was generally administered for 4-8 weeks; some involved comparisons with nonsteroidal anti-in­flammatory drugs (NSAIDs).

For osteoarthritis, four double-blind, controlled clinical trials have been published. In two placebo-controlled studies (n = 50, 100), treatment with 2.4 g/day of devil's claw dried root or stan­dardized extract produced a statistically significant reduction of pain compared to placebo. Another randomized placebo-con­trolled trial reported improvement in pain and spinal mobility with a dose of 2 g/day in 89 patients with joint pain. 1o The largest study (n = 122) compared the efficacy of devil's claw to diacerhein, a European non-NSAID drug for osteoarthritis. Devil's claw (2.6 g/day root powder) was as effective as standard doses of diacer­hein for treatment of hip or knee osteoarthritis, but the reduction of pain and functional disability did not reach statistical signifi­cance for either group. There was a statistically significant reduc­tion in the need for analgesic and NSAID medication in the devil's claw group compared to the diacerhein group.

Adverse Effects:

Devil's claw appears to be well tolerated. Most clinical trials reported no side effects other than occasional cases of mild gastrointestinal upset. One patient withdrew from an uncontrolled clinical study reporting a throbbing frontal headache, tinnitus, anorexia, and loss of taste.

Side Effects and Interactions:

There are no well-documented drug interactions. A theoretical concern about interactions with warfarin, and NSAIDs and other antiplatelet agents, has been raised in the literature. This is based based on one case report of purpura in a patient receiving warfarin and devil's claw; details of this case are unknown. However, no hematologic problems have been observed in clinical trials or in animal models. Anti-arrhythmic effects demonstrated in animal experiments suggest that caution is advisable in using devil's claw with anti-arrhythmics and cardiac glycosides.

Cautions:

Herbal authorities advice caution when using devil's claw (considered a "bitter" herb, which is thought to stimulate gastric acid) in the presence of peptic ulcers, although this potential effect has not been reported or evaluated. Devil's claw is best avoided in pregnancy due to oxytoxic effects in animals. Its safety has not been evaluated during pregnancy or lactation.

Preparations & Doses

Traditionally, 3-6 g/day of dried root is taken in three divided doses for analgesic and anti-inflammatory activity. A smaller daily dose of 0.5-1.5 g has been recommended for anorexia. Clinical trials for pain relief have used doses ranging as low as 0.75-2.6 g/day of dried root, but most studies used extracts corresponding to about 3-6 g/day (2-2.4 g/day of a 2.5:1 solid extract, or 0.6-1.2 g/day of a 5: 1 powdered extract). Liquid preparations are taken as teas, tinctures, or fluid extracts. Some devil's claw products are standardized to harpagoside.

Summary Evaluation:

Devil's claw has traditionally been employed to treat joint pain and digestive problems and appears to be relatively well tolerated.