Herbal medicines for asthma: a systematic review (2000; 55: 925-9)
Despite their widespread use among asthmatics, there is little definitive evidence that herbal medicines reduce asthma symptoms, shows research in Thorax. A recent survey from the National Asthma Campaign indicates that around two thirds of those with mild asthma and around three quarters of those with severe symptoms use herbal remedies.
The researchers trawled through four major medical research databases for published trials of herbal medicines used in the treatment of asthma. They found 17 clinical trials, six of which dealt with traditional Chinese medicines, and eight of which described Indian Ayurvedic medicines. Three other trials looked at a Japanese Kampo medicine, marijuana, and dried ivy leaf extract.
Analysis of the data showed that most of the trials were of poor quality and lacked criteria required for a thorough scientific appraisal, say the authors. And among those that indicated some positive benefits, the flaws were such to cast doubt on the validity of the results. "There is no fully convincing evidence for any of the herbal preparations described," they say.
Furthermore, they caution that none of the herbal remedies referred to is likely to be free of side-effects and some adversely interfere with prescribed drugs. The authors cite Gingko biloba, widely considered to be one of the safest of herbal medicines, as having a range of possible side-effects and well as the potential to interfere with anticoagulant drugs.
Properly designed research is urgently needed to assess the real safety and treatment value of herbal medicines for asthma, conclude the authors.
Contact:
Dr Alyson Huntley, Department of Complementary Medicine, School of Postgraduate Medicine and Health Studies, University of Exeter.
Tel: 01392 424 872
Fax: 01392 424 989
A.Huntley@ex.ac.uk
Journal
Thorax