Overall, current evidence from clinical trials suggest that devil's claw may be a useful treatment for arthritis; however, it is suggested, as with many herbal medicines, that evidence of effectiveness is not transferrable from product to product and that the evidence is more robust for products that contain at least 50 mg of harpagoside in the daily dosage (Chrubasik et al 2003a, Gagnier et al 2004).
An observational study of 6 months' use of 3-9 g/day of an aqueous extract of devil's claw root reported significant benefit in 42-85% of the 630 people suffering from various arthritic complaints (Bone & Walker 1997). In a 12-week uncontrolled multicentre study of 75 patients with arthrosis of the hip or knee, a strong reduction in pain and the symptoms of osteoarthritis were observed in patients taking 2400 mg of devil's claw extract daily, corresponding to 50 mg harpagoside (Wegener & Lupke 2003). Similar results were reported in a 2-month observational study of 227 people with osteoarthritic knee and hip pain and non-specific low back pain (Chrubasik et al
2002) and a double-blind study of 89 subjects with rheumatic complaints using powdered devil's claw root (2 g/day) for 2 months, which also provided significant pain relief, whereas another double-blind study of 100 people reported benefit after 1 month (Bone & Walker 1997). A case report suggests that devil's claw relieved strong joint pain in a patient with Crohn's disease (Kaszkin et al 2004).
Comparisons with standard treatment have also been investigated. In 2000, encouraging results of a randomised double-blind study comparing the effects of treatment with devil's claw 2610 mg/day with diacerhein 100 mg/day were published (Leblan et al 2000). The study involved 122 people with osteoarthritis of the hip and/or knee and was conducted over 4 months. It found that both treatment groups showed similar considerable improvements in symptoms of osteoarthritis; however, those receiving devil's claw required fewer rescue analgesics.
One double-blind, randomised, multicentre clinical study of 122 patients with osteoarthritis of the knee and hip found that treatment with Harpadol (6 capsules/day, each containing 435 mg of cryoground powder of H. procumbens) given over 4 months was as effective as diacerhein (an analgesic) 100 mg/day (Chantre et al 2000). However, at the end of the study, patients taking Harpadol were using significantly fewer NSAIDs and had a significantly lower frequency of adverse events. In a 6-week study of only 13 subjects, similar benefits for devil's claw and indomethacin were reported (Newall et al 1996). A recent preliminary study comparing the proprietary extract Doloteffin with the COX-2 inhibitor, rofecoxib, reported a benefit with the herbal treatment but suggested that larger studies are still required (Chrubasik et al 2003b). The herb is Commission E approved as supportive therapy for degenerative musculoskeletal disorders (Blumenthal et al 2000) and ESCOP approved for painful osteoarthritis (ESCOP 2003).
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