Devil's claw, derived from the roots of a South African plant, has been available over the counter for some time, sold to consumers searching for an alternative to the nonsteroidal anti-inflammatory drugs (NSAIDs) commonly prescribed by doctors to help relieve arthritis pain. These have serious side effects.
The global market currently uses between 600 and 700 metric tons of raw material each year, according to German company Martin Bauer, which has recently begun harvesting what it claims is the first specially cultivated crop. Sales of the extract in Germany alone were worth €8 million in 1999, rising 113 per cent the next year and 59 per cent in 2001 to €27 million, according to Phytopharm Consulting. In 2002 it was worth €31 million.
But researchers at the UK-based University of Southampton's Complementary Medicine Research Unit say they need more data on the optimum dose required, as well as long-term safety and efficacy.
"There have been a number of studies on the plant but some of these are only observational and the double-blind, randomized trials were mostly small," said Dr Sarah Brien, the principal researcher.
The Southampton researchers are aiming to recruit 260 patients with knee osteoarthritis aged over 40. "This is a large study that is powered to give us a definite answer on the efficacy of devil's claw," said Dr Brien.
She added that previous trials looking at efficacy had not been carried out for more than six weeks, whereas clinically a patient will take this for two to three months. Patients in the new placebo-controlled study will be on one of three different dosage levels to assess the optimum dose required and the long-term safety of the supplement.
"Often patients take it in conjunction with conventional treatments so we want to look at whether this is reasonable," she added.
Other ingredients commonly taken in supplement form for osteoarthritis include glucosamine, sales of which are thought to be rising by around 10 per cent annually. Consumption of glucosamine is much higher than devil's claw at between 4,000-6,000 tons annually but the ingredient is currently facing a major supply shortage.