BACKGROUND:Devil's claw is a plant that grows in southern Africa and is also called the wood spider or grapple plant. The names come from its strange-looking fruit from which long barbs emanate. The plant has a long tradition of medicinal use for many conditions, particularly pain relief. Extracts are made from the underground tubers, which look like sweet potatoes. These herbal remedies have been studied extensively, with their use in the relief of low-back pain emerging as a promising application.
EVIDENCE FROM STUDIES
A systematic review was published earlier this year that investigated various herbal remedies used for painful rheumatic conditions. Few herbs were found to be effective, but devil’s claw for low-back pain showed most promise. Numerous laboratory studies have shown that extracts of devil’s claw contain anti-inflammatory agents. The best studied of these is a substance called harpagoside, which gets its name from the scientific name for devil’s claw: Harpagophytum procumbens. The genus comes from the Greek for “hook plant”. Some commercial products are standardised to contain a specified amount of harpagoside, although the amount in different brands varies widely.
Several randomised controlled trials of devil’s claw for low-back pain were identified in the systematic review. Of these, four were of high quality and moderate size. All of these used a commercial devil’s claw product called Doloteffin, which is an aqueous extract standardised to contain 50mg harpagoside. The research subjects had chronic, non-specific low-back pain. Two trials found Doloteffin significantly more effective in reducing pain than a placebo.
One trial found that devil’s claw had the same pain-relieving effect as some conventional therapies recommended by physicians. The fourth found Doloteffin to be similarly effective to Vioxx, a conventional pain-relieving drug that has since been withdrawn from the market. The most common dose used in these studies was 50mg per day. One study found that 100mg was more effective than 50mg, but the number of subjects was too small to be statistically reliable.
A limitation with all these studies is that they lasted only four or six weeks. While the results were encouraging, a chronic condition like low-back pain should be studied for longer.
The most recent study in this area monitored patients for a year after the conclusion of one of the randomised studies. All the participants knew they were taking devil’s claw and were asked to complete detailed journals. Over the year, people reported that their pain remained under control, they rarely used other pain relievers and they had few adverse effects. However, the lack of a control group is a major limitation with this study, especially for a condition like back pain that varies naturally.
PROBLEMATIC ASPECTS
Devil’s claw does not appear to cause serious adverse effects. A review of all controlled trials found that 20 had studied its adverse effects. Overall, similar problems were reported by those taking a placebo and devil’s claw. Mild gastrointestinal problems were most commonly reported, such as diarrhoea, nausea and vomiting.
RECOMMENDATIONS
Low-back pain is a common condition with a wide range of severity. Depending on the cause of the problem, various combinations of exercise, weight loss, physiotherapy and medication can help. Conventional pain killers are readily available and effective, but can have adverse effects, especially if taken long term.
Devil’s claw has good evidence of benefit for chronic, generalised low-back pain. However, the evidence is primarily available for short-term use. Most of the evidence is available for one water extract, while alcohol extracts are also available. It is unclear whether 50 or 100mg daily is most effective. Given the available evidence, a trial period with devil’s claw may be helpful with low-back pain. Since back pain can have many possible causes, further professional advice should be sought if the condition does not improve within a few weeks.
Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University