The Pharmaceutical Journal
Vol 269 No 7229 p881
21/28 December 2002

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Annals of Internal Medicine: Editorial (more)

Use of echinacea to treat the common cold warrants further investigation

Although it is difficult to ignore the widespread use and persistent anecdotal reports of the benefits of echinacea, scientific evidence of its efficacy remains unconvincing. Nevertheless, the evaluation of echinacea as a treatment option for the common cold should continue to be investigated, according to Dr Ronald Turner, University of Virginia School of Medicine, Charlottesville.

In an editorial published in Annals of Internal Medicine, Dr Turner says that methodological flaws in studies have limited the acceptance of reported beneficial effects of various echinacea preparations on the common cold. The fact that different preparations of echinacea have different compositions has meant definitive studies have been difficult to perform.

Dr Turner also points out that neither the active component of echinacea nor its mechanism of action for treating the common cold have been defined.

"Unless an active constituent or combination of constituents can be identified or a desired biological activity defined, we cannot address such fundamental issues as dosing, bioavailability or pharmacokinetics," he says (2002;137:1001). In the same issue of Annals of Internal Medicine, researchers report that in a study of 148 subjects with recent onset common colds, unrefined echinacea provided no detectable benefit or harm, compared with placebo.

They assigned those in the echinacea group to receive an encapsulated mixture of unrefined Echinacea purpurea herb (25 per cent) and root (25 per cent) and Echinacea angustifolia root (50 per cent) taken in 1g doses six times on the first day of illness and then three times daily on each subsequent day of illness for a maximum of 10 days.

The preparation was found to have no effect on the duration or severity of symptoms, contradicting current published evidence, the researchers say. However, the preparation used had not been tested previously and may be ineffective because of bioavailability or phytochemical constituents. Also, the population studied, healthy undergraduate college students, may be among those who might not gain much benefit from echinacea (ibid, p939).

Dr Jo Barnes, lecturer in phytopharmacy, School of Pharmacy, University of London, told The Journal: "This is not the end of the story for echinacea, more a twist in the tale." The results of the study should not be extrapolated to other preparations of echinacea which have different phytochemical composition. She added: "Clearly, further research with well-defined preparations of echinacea are needed to determine whether they are efficacious in treating symptoms of the common cold".