Devil's claw

What it is

Devil's claw is the cut and dried tuberous secondary root of two southern African plants, Harpagophytum procumbens and Harpagophytum zeyheri. The European Pharmacopoeia requires the dried root to contain at least 1.2% harpagoside. Its characteristic constituents are bitter iridoid glucosides, principally harpagoside, alongside 8-(p-coumaroyl)-harpagide and smaller amounts of harpagide and procumbide. Supplements are made as aqueous or hydroalcoholic dry extracts standardised to harpagoside.

What the research says

Devil's claw is used for musculoskeletal pain. A Cochrane review of herbal medicine for low back pain found that standardised daily doses of 50 mg or 100 mg harpagoside may reduce pain more than placebo, with overall evidence quality ranging from very low to moderate. An earlier systematic review graded the low back pain evidence as moderate to strong but the osteoarthritis evidence as only limited, and a Cochrane review of herbal therapies in osteoarthritis was explicitly uncertain about products other than Boswellia and avocado-soybean unsaponifiables. Reported harms are mostly mild gastrointestinal upset, and European regulators contraindicate it in active peptic ulcer.

Evidence grade: Limited evidence.

What goes wrong

Adverse effects reported in herbal low back pain trials, including devil's claw trials, were mostly mild transient gastrointestinal complaints or skin irritation. (Source 1)

• Systematic review, Low certainty.
• Size: 14 studies, 2050 adults.
• Who: Adults with low back pain.
• How long: Typically three weeks.
• Result: No rates given in the summary; effects characterised as mild and transient.
• Funding: not stated.

Adverse effects were reported, but appeared to be primarily confined to mild, transient gastrointestinal complaints or skin irritations.

The European Medicines Agency's herbal monograph records gastrointestinal, central nervous system and hypersensitivity reactions for devil's claw root, with frequency unknown. (Source 2)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: Users of authorised devil's claw root products.
• How long: not applicable.
• Result: Frequency stated as not known for all listed reactions.
• Funding: not stated.

Gastrointestinal symptoms (diarrhoea, nausea, vomiting, abdominal pain) have been reported.

The European Medicines Agency contraindicates devil's claw root in patients with active gastric or duodenal ulcer. (Source 3)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: People with active peptic ulcer disease.
• How long: not applicable.
• Result: Absolute contraindication, no rate given.
• Funding: not stated.

Limit of this finding: The monograph prints sections 4.3 and 4.4 as a two-column table, one column for 'well-established use' preparations and one for 'traditional use' preparations, and a warning can belong to one column only. The machine-readable text flattens the table, and repeated readings disagreed about which column some warnings sit in, so it could not be established here whether every warning applies to every devil's claw preparation. Treat these as warnings the regulator attaches to devil's claw root products, and check the monograph table itself before applying one to a specific product.

Hypersensitivity to the active substance. Patients with active gastric or duodenal ulcer.

The same monograph advises that people with gallstones consult a physician first, and states that use in under-18s has not been established. (Source 3)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: People with gallstones; children and adolescents under 18.
• How long: not applicable.
• Result: Precautionary statements, no rates given.
• Funding: not stated.

Limit of this finding: The monograph prints sections 4.3 and 4.4 as a two-column table, one column for 'well-established use' preparations and one for 'traditional use' preparations, and a warning can belong to one column only. The machine-readable text flattens the table, and repeated readings disagreed about which column some warnings sit in, so it could not be established here whether every warning applies to every devil's claw preparation. Treat these as warnings the regulator attaches to devil's claw root products, and check the monograph table itself before applying one to a specific product. On the readings obtained, the gallstone advice appears in the traditional-use column, while the statement about under-18s applies to the well-established-use column as well.

Patients with gallstones should consult a physician prior to use devil's claw.

What the evidence supports

A Cochrane review of herbal medicine for low back pain found that devil's claw at standardised daily doses of 50 mg or 100 mg harpagoside may reduce pain more than placebo. (Source 1)

• Systematic review, Moderate certainty.
• Size: 14 studies, 2050 adults across six herbal medicines.
• Who: Adults with low back pain, average age 52 years.
• How long: Studies typically three weeks.
• Result: Pain reduction greater than placebo at 50 mg and 100 mg harpagoside daily; 60 mg daily reduced pain about the same as 12.5 mg of rofecoxib.
• Funding: not stated.

Devil's claw, in a standardized daily dose of 50 mg or 100 mg harpagoside, may reduce pain more than placebo; a standardized daily dose of 60 mg reduced pain about the same as a daily dose of 12.5 mg of Vioxx®.

An earlier systematic review graded the evidence as strong only for an aqueous extract at 50 mg harpagoside daily in acute exacerbations of chronic non-specific low back pain. (Source 4)

• Systematic review, Moderate certainty.
• Size: 12 trials, of which six in osteoarthritis, four in low back pain and three in mixed pain conditions.
• Who: Adults with osteoarthritis, low back pain or mixed pain.
• How long: Short term.
• Result: Strong evidence at 50 mg harpagoside daily; moderate evidence at 60 mg powder and at 100 mg aqueous extract; 60 mg non-inferior to 12.5 mg rofecoxib in the short term.
• Funding: not stated.

Strong evidence exists for the use of an aqueous Harpagophytum extract at a daily dose equivalent of 50 mg harpagoside in the treatment of acute exacerbations of chronic NSLBP.

What the evidence does not support

The same review found only limited evidence for a lower-dose ethanolic extract in knee and hip osteoarthritis. (Source 4)

• Systematic review, Low certainty.
• Size: 12 trials, six of them in osteoarthritis.
• Who: Adults with knee and hip osteoarthritis.
• How long: Short term.
• Result: Graded as limited evidence for ethanolic extract containing under 30 mg harpagoside per day.
• Funding: not stated.

There is limited evidence for an ethanolic Harpagophytum extract containing less than <30 mg harpagoside per day in the treatment of knee and hip osteoarthritis.

A Cochrane review of oral herbal therapies for osteoarthritis was uncertain whether herbal products other than Boswellia serrata and avocado-soybean unsaponifiables improve osteoarthritis pain or function. (Source 5)

• Systematic review, Very low certainty.
• Size: Evidence limited to single studies or studies that could not be pooled.
• Who: People with osteoarthritis.
• How long: not stated.
• Result: No pooled estimate; evidence described as limited and some studies low to very low quality; quality of life not measured.
• Funding: not stated.

We are uncertain whether other oral herbal products improve osteoarthritis pain or function, or slow progression of joint structure damage because the available evidence is limited to single studies or studies that cannot be pooled, and some of these studies are of low to very low quality.

Where the evidence is mixed

The same Cochrane review rated the overall quality of the herbal low back pain evidence as mainly very low to moderate. (Source 1)

• Systematic review, Very low certainty.
• Size: 14 studies, 2050 adults.
• Who: Adults with low back pain.
• How long: Typically three weeks.
• Result: Quality of evidence mainly very low to moderate despite most trials being at low risk of bias.
• Funding: not stated.

Most included trials were at low risk of bias and the quality of the evidence was mainly very low to moderate.

Where the research disagrees

Whether devil's claw works for osteoarthritis as opposed to low back pain

• Gagnier and colleagues, BMC Complementary and Alternative Medicine, 2004, systematic review of 12 trials: There is moderate evidence of effectiveness for (1) the use of a Harpagophytum powder at 60 mg harpagoside in the treatment of osteoarthritis of the spine, hip and knee (Source 4)
• Cochrane review of oral herbal therapies for osteoarthritis, 2014, systematic review with GRADE: We are uncertain whether other oral herbal products improve osteoarthritis pain or function, or slow progression of joint structure damage because the available evidence is limited to single studies or studies that cannot be pooled, and some of these studies are of low to very low quality. (Source 5)

How much

• Reference intake: No reference intake exists; devil's claw is a medicinal root, not a nutrient. The only quantitative standard is pharmacopoeial content, with the dried root required to contain at least 1.2% harpagoside. (Source 6)
• Upper limit: No tolerable upper intake level or acceptable daily intake was found in the sources reached. The EMA monograph sets permitted daily doses for authorised products and states that use in children and adolescents under 18 has not been established, rather than defining a safety ceiling. (Source 3)
• Studied: Cochrane reported trials using standardised daily doses of 50 mg or 100 mg harpagoside, and a 60 mg daily dose compared with 12.5 mg rofecoxib. (Source 1)
• Studied: An earlier systematic review described a Harpagophytum powder providing 60 mg harpagoside a day in osteoarthritis of the spine, hip and knee. (Source 4)

A common belief, and what the research shows

The belief: Devil's claw is a gentle natural painkiller that anyone can take instead of an anti-inflammatory drug.

What the research shows: European regulators contraindicate it outright in active peptic ulcer, the same population in whom NSAIDs are avoided, and list gastrointestinal, neurological and hypersensitivity reactions of unknown frequency: 'Gastrointestinal symptoms (diarrhoea, nausea, vomiting, abdominal pain) have been reported.' The comparison with an NSAID is also narrower than it sounds: Cochrane reports only that 'a standardized daily dose of 60 mg reduced pain about the same as a daily dose of 12.5 mg of Vioxx®.' in short trials averaging three weeks.

Questions and answers

What is it?

Devil's claw is the dried secondary tuber of Harpagophytum procumbens or Harpagophytum zeyheri, plants of southern Africa. The pharmacopoeial root must contain at least 1.2% harpagoside. Supplements are dry extracts of that root, made with water or alcohol. (Source 6)

What does it do in the body?

The root's characteristic compounds are bitter iridoid glucosides, chiefly harpagoside, along with 8-(p-coumaroyl)-harpagide and small amounts of harpagide and procumbide. These are what preparations are standardised to. The dose in trials is expressed as milligrams of harpagoside rather than milligrams of root. (Source 6)

Is it good or bad for you?

For short-term low back pain the Cochrane evidence points to a pain reduction over placebo at standardised harpagoside doses, though the overall certainty runs from very low to moderate and trials averaged about three weeks. For osteoarthritis the picture is far less settled. It is contraindicated in active peptic ulcer, so it is not benign for everyone. (Source 1)

How do you get more of it?

It is taken as a standardised root extract, dosed by harpagoside content rather than by weight of root. Trials have used aqueous extracts delivering 50 mg or 100 mg harpagoside a day, and a powder delivering 60 mg a day. It is not obtained from food. (Source 4)

If it is harmful, what reduces it?

Devil's claw is not stored in the body, so exposure ends when the preparation is stopped. Where it causes harm the reported problems are mostly gastrointestinal, and European regulators list diarrhoea, nausea, vomiting and abdominal pain as reported reactions of unknown frequency, with stopping the product the obvious response. (Source 2)

Why might someone be low in it or missing it?

Does not apply. Devil's claw is not a nutrient and there is no deficiency state, so nobody can be low in it. Some groups are deliberately kept away from it instead: European regulators say its use in people under 18 has not been established because the data are inadequate. (Source 3)

Which whole foods contain it or feed it?

No whole food contains it and nothing in the diet feeds it. It comes only from the dried secondary tuber of a southern African plant, supplied as a standardised extract whose harpagoside content is defined by pharmacopoeial specification. (Source 6)

What happens if you do not have it?

Nothing happens, because devil's claw is not essential to the body. Not taking it means forgoing a short-term pain option whose effect in osteoarthritis Cochrane reviewers were explicitly uncertain about. (Source 5)

How can you test for it?

There is no clinical test for devil's claw status in a person. The only measurement in the literature is chemical analysis of the product itself, where the European Pharmacopoeia requires the dried root to contain at least 1.2% harpagoside and the dry extract at least 1.5%. That is a potency specification for the active constituent, not a test of purity, and no contamination or adulteration testing of devil's claw products was found in the sources reached. (Source 6)

We searched: Searched the EMA assessment report and herbal monograph on Harpagophytum, the 2014 Cochrane review of herbal medicine for low back pain, the 2014 Cochrane review of oral herbal therapies for osteoarthritis and the 2004 BMC systematic review for any biomarker, blood level or diagnostic test; only product content specifications are described.

References

1. Cochrane Database of Systematic Reviews / Cochrane. Herbal medicine for low-back pain (plain language summary). 2014. PMID 25536022, DOI 10.1002/14651858.CD004504.pub4. Read the source
2. European Medicines Agency, Committee on Herbal Medicinal Products. European Union herbal monograph on Harpagophytum procumbens DC. and/or Harpagophytum zeyheri Decne., radix (Interactions and undesirable effects). 2016. Read the source
3. European Medicines Agency, Committee on Herbal Medicinal Products. European Union herbal monograph on Harpagophytum procumbens DC. and/or Harpagophytum zeyheri Decne., radix (Contraindications and warnings). 2016. Read the source
4. BMC Complementary and Alternative Medicine. Harpagophytum procumbens for osteoarthritis and low back pain: a systematic review. 2004. PMID 15369596, DOI 10.1186/1472-6882-4-13. Read the source
5. Cochrane Database of Systematic Reviews / Cochrane. Oral herbal therapies for treating osteoarthritis (Quality of the evidence). 2014. PMID 24848732, DOI 10.1002/14651858.CD002947.pub2. Read the source
6. European Medicines Agency, Committee on Herbal Medicinal Products. Assessment report on Harpagophytum procumbens DC. and/or Harpagophytum zeyheri Decne., radix (herbal substance and constituents). 2016. Read the source