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No good evidence exists that individually tailored prescriptions of a mixture of herbs are effective, concludes a systematic review published last week.
The study reviewed all available studies of individualised herbal medicine for any indication (Postgraduate Medical Journal 2007;83:633-7). The researchers, from the Universities of Exeter and Plymouth, found only three randomised controlled trials out of 1300 studies they identified that they considered were of sufficient quality to draw meaningful conclusions. These three trials showed no convincing evidence of benefit.
One trial, involving patients with osteoarthritis of the knee, showed a non-significant trend favouring active treatment over placebo. However, the researchers said that this trend probably resulted from large differences at baseline and regression to the mean.
In a trial of patients with irritable bowel syndrome, individualised herbal treatment was better than placebo in four of the five outcomes tested but was inferior to a standardised herbal treatment (a mixture of herbs not tailored to the individual) in all outcomes.
In the third trial they looked at, individualised herbal treatment was no better than placebo in preventing chemotherapy induced toxicity.
The researchers warned: “Individualised herbal medicine, as practised in European medical herbalism, Chinese herbal medicine, and Ayurvedic herbal medicine, has an extremely sparse evidence base and there is no evidence supporting its use in any indication.
“The paucity of data supporting the effectiveness of individualised herbal medicine, and the important safety concerns associated with this particular form of phytomedicine, should be taken into account by policymakers concerned with the regulation of practitioners using this modality.”
In an accompanying editorial Edzard Ernst, professor of complementary medicine at the Peninsula Medical School at the University of Exeter, considered that the public was in danger of confusing different types of herbal medicine.
He explained that phytotherapy (plant therapy practised by a health practitioner), which includes use of specific herbs, such as St John's wort, that contain a range of pharmacologically active ingredients and for which data on effectiveness are “reasonable,” is often confused with traditional herbal medicine, in which practitioners prescribe individual mixtures of herbs and over the counter remedies that are based on plants and sold as dietary supplements.
Professor Ernst argued that properly conducted clinical trials should be carried out as part of improving the regulation of herbal medicines. He concluded: “Phytotherapy has considerable potential to benefit patients. But over the counter remedies and traditional herbal medicine can harm those who use them.”