Devil's Claw (Harpagophytum procumbens) as a treatment for osteoarthritis: a review of efficacy and safety

BACKGROUND: Osteoarthritis (OA) is a highly prevalent musculoskeletal disorder. Conventional treatment (i.e., the use of nonsteroidal anti-inflammatory drugs-NSAIDs) is associated with well-documented adverse effects. Devil's Claw (Harpagophytum procumbens) a traditional South African herbal remedy used for rheumatic conditions, may be a safer treatment option. To date, 14 clinical trials have assessed its efficacy/ effectiveness in OA. AIM: To address the two main questions of importance to clinicians: (1) Does Devil's Claw work for the treatment of OA, and (2) Is it safe? METHODS: A review of the literature on Devil's Claw and OA from 1966 to 2006 was performed using multiple search databases, monographs, and citation tracking. Relevant trials in all languages were identified and included. Both internal validity (i.e., adequacy of the dosage and period of treatment for this condition, reporting of randomization, rates of dropout, blinding, and statistical analysis) and external validity (i.e., inclusion/ exclusion criteria, baseline characteristics of the study populations, trial setting, and the appropriateness of the outcome measures of the trials) were assessed. RESULTS: Fourteen studies were identified: eight observational studies; 2 comparator trials (1 open, the other randomized to assess clinical effectiveness); and 4 double-blinded, placebo-controlled, randomized controlled trials to assess efficacy. Many of the published trials lacked certain important methodological quality criteria. However, the data from the higher quality studies suggest that Devil's Claw appeared effective in the reduction of the main clinical symptom of pain. The assessment of safety is limited by the small populations generally evaluated in the clinical studies. From the current data, Devil's Claw appears to be associated with minor risk (relative to NSAIDs), but further long-term assessment is required. CONCLUSIONS: The methodological quality of the existing clinical trials is generally poor, and although they provide some support, there are a considerable number of methodologic caveats that make further clinical investigations warranted. The clinical evidence to date cannot provide a definitive answer to the two questions posed: (1) Does it work? And (2) is it safe? A definitive high-quality trial that addresses the necessary methodologic improvements noted is needed to answer these important clinical questions.