Benefits
Hip and knee joint comfort and mobility
In a 4-month double-blind trial in 122 adults with hip or knee osteoarthritis, root powder (2,610 mg a day) was compared with a prescription drug rather than placebo. Pain and function scores improved over time in the devil's claw group, but without a placebo group the trial cannot show how much of that came from the root. Reviews rate most osteoarthritis studies as small or uncontrolled.
Lower back comfort during flare-ups
In a 4-week trial in 197 adults with flare-ups of chronic low back pain, more people became pain free on extract giving 100 mg harpagoside a day (10) or 50 mg (6) than on placebo (3). An earlier 118-person trial missed its main goal, rescue painkiller use. A Cochrane review rated this evidence low quality for short-term relief.
Back, shoulder and neck muscle comfort
In a 4-week double-blind trial in 63 adults with slight to moderate muscle tension or slight muscle pain in the back, shoulders and neck, extract LI 174 (480 mg twice daily) did better than placebo on pain ratings, pressure sensitivity and a muscle stiffness test, while muscle reflexes and EMG activity did not differ. It is one small trial that has not been repeated.
Knee comfort with a rose hip, nettle and devil's claw formula
In a 12-week placebo-controlled trial in 92 adults with knee osteoarthritis, a daily drink combining rose hip, nettle leaf and devil's claw root extract with vitamin D improved WOMAC pain scores more than placebo (about 30 vs 10 points). Because it was a mix, the share due to devil's claw is unknown, and a firm linked to the sponsor ran the study.
Tolerability in the trials
A safety review of 28 clinical trials found minor side effects, mostly digestive, in about 3% of people, and no double-blind study in which side effects were more common than on placebo. Because most trials used doses at the lower end of the range and people may take it long term, the reviewers called for more safety data.
Mechanism of action
Harpagoside as the standardization marker
Products are standardized to harpagoside, but reviewers found that results do not transfer from one devil's claw product to another. Evidence was better for products giving at least 50 mg harpagoside a day than for lower-dose ethanol extracts, so the harpagoside amount on the label matters more than the root weight.
Inflammation pathways in lab studies
Laboratory and animal studies suggest harpagoside may act on inflammation signals such as COX-2, NF-kB and pro-inflammatory cytokines. A recent review stresses that these are indirect findings; the human trials cited here measured pain and function, not inflammation markers.
Peripheral effects on muscle pain sensitivity
In the muscle-tension trial, the extract changed pressure-pain thresholds, a muscle stiffness test and a muscle ischemia test but not pain-related muscle reflexes or EMG activity. The authors found no central nervous system effects and read the results as an action on muscle tissue, a finding from one small trial.
Clinical trials
Cochrane systematic review of 14 randomized controlled trials of herbal medicines for non-specific low back pain, with GRADE quality ratings; three trials tested oral devil's claw (Oltean et al. 2014, Cochrane Database Syst Rev)
2,050 adults across 14 trials; the devil's claw comparisons involved 315 people in two placebo-controlled trials and 88 in one trial against a prescription painkiller.
Daily devil's claw doses standardized to 50 or 100 mg harpagoside may be better than placebo for short-term pain and may reduce rescue medicine use, but the reviewers rated this low quality evidence. The trial against a prescription painkiller was rated very low quality, so it cannot show the two are equivalent. No significant adverse events were noted.
Randomized, placebo-controlled, double-blind 4-week trial of extract WS 1531 at 600 or 1,200 mg a day, providing 50 or 100 mg harpagoside (Chrubasik et al. 1999, Eur J Anaesthesiol)
197 adults with chronic low back pain and a current flare-up rated above 5 out of 10; 183 completed.
The number of people who were pain free without rescue tramadol on at least 5 days of the last week was 3 on placebo, 6 on 50 mg harpagoside and 10 on 100 mg (P = 0.027, one-tailed test). Subgroup and secondary analyses gave inconsistent pictures of who benefited most. Only mild, infrequent digestive symptoms were possibly linked to the extract.
Randomized, double-blind, placebo-controlled 4-week trial of an extract providing 50 mg harpagoside a day, taken as two tablets three times daily (Chrubasik et al. 1996, Phytomedicine)
118 adults with chronic back problems seeking treatment for acute pain; 109 completed.
The planned main outcome, use of rescue tramadol over the last 3 weeks, did not differ between groups. In further analysis, 9 of 51 people on the extract were pain free at the end versus 1 of 54 on placebo, and a back-pain index improved more on the extract, but that difference fell just short of conventional statistical significance. No adverse effects were shown.
Randomized, double-blind, placebo-controlled 4-week trial of extract LI 174, 480 mg twice daily; article in German (Göbel et al. 2001, Schmerz)
63 adults with slight to moderate muscle tension or slight muscle pain of the back, shoulder and neck (31 extract, 32 placebo).
Compared with placebo, the extract improved pain ratings, pressure-pain thresholds, a muscle stiffness test, a muscle ischemia test and patient and physician global ratings. Muscle reflexes and EMG surface activity did not differ. Tolerability was good, with no serious adverse effects. It was one small trial.
Double-blind, randomized, multicentre 4-month trial of root powder (Harpadol, 6 capsules of 435 mg a day) against the prescription drug diacerhein 100 mg a day, lead author affiliated with Laboratoires Arkopharma (Chantre et al. 2000, Phytomedicine)
122 adults with osteoarthritis of the knee or hip.
Pain and the Lequesne function index improved over the 4 months in both groups, with no difference between them. The devil's claw group used fewer NSAIDs and rescue painkillers and had significantly fewer adverse events; diarrhea, the most common, occurred in 8.1% vs 26.7%. Without a placebo group the trial cannot show how much of the improvement was due to the root itself.
Randomized, placebo-controlled, double-blind 12-week trial of a daily 40 mL drink (MA212) of rose hip, nettle leaf and devil's claw root extract with vitamin D; planned and analysed by a firm affiliated with the sponsor (Moré et al. 2017, Planta Med)
92 adults with knee osteoarthritis (46 formula, 44 placebo).
The WOMAC pain score, the main outcome, improved by 29.87 points on the formula and 10.23 points on placebo (P < 0.001), and quality-of-life scores also improved more on the formula. Because devil's claw was one of several ingredients, the trial cannot show what it contributed on its own.
Open, uncontrolled surveillance study of the extract Doloteffin at 60 mg harpagoside a day for up to 54 weeks (Chrubasik et al. 2007, Phytomedicine)
114 adults: 56 with chronic low back pain, 37 with knee osteoarthritis and 21 with hip osteoarthritis pain.
Most symptom scores fell over the year in all three groups, rescue painkiller use declined, and 75% met response criteria. Adverse events were few and none were serious. With no control group, these changes cannot be separated from natural fluctuation or expectation, but the study adds some longer-term tolerability data.