Herbal medicines for asthma: a systematic review

A survey by the National Asthma Campaign found that 60% of people with moderate asthma and 70% with severe asthma have used complementary and alternative medicine to treat their condition. 1 Herbal medicine is the third most popular choice of both adults (11%) and children (6%) suffering from asthma. 1

The historical importance of herbal medicine in the treatment of asthma is indisputable. Four of the five classes of drugs currently used to treat asthma-namely, [beta]₂ agonists, anticholinergics, methylxanthines and cromones-have origins in herbal treatments going back at least 5000 years. 2

There is a large archive of information on herbal medicine from many cultures for the treatment of asthma. However, a significant proportion of these reports is not based on adequately designed trials. This review provides a critical analysis of herbal medicinal products used in the treatment of asthma symptoms that have been the subject of randomised clinical trials.

Methods

Computerised literature searches were performed to identify all published articles on the subject. The following databases were used: Medline, Pubmed, Cochrane Library, and Embase, all from their inception to December 1999. Search terms used were "asthma", "herb*", "Ayurvedic", and "traditional Chinese medicine", as well as any individual herb name cited in the asthma literature. In addition, other researchers in this field were asked for further papers and our own files were searched. The bibliographies of all papers thus located were searched for further relevant articles. Only randomised clinical trials (parallel and crossover) were included. There were no restrictions regarding publication language. All articles were read in full and data extracted in a predefined fashion by the first author. All trials were rated according to methodological rigour using the Jadad score (table 1 ). 3

1. Study described as ramdomised (this includes the use of words such as "random", "randomly" and "randomisation")

2. Study described as double blind?

3. Description of withdrawals and dropouts?

4. Method to generate the sequence of randomisation described and appropriate (table of random numbers, computer generated, etc)?

5. Method of double blinding described and appropriate (identical placebo, active placebo, dummy etc)?

6. Method to generate the sequence of randomisation described and inappropriate (patients were allocated alternately or according to their date of birth, hospital number, etc).

7. Method of...