Background: Chinese herbal medicine is frequently used for treating diabetic peripheral neuropathy in China. Many controlled trials have been undertaken to investigate its efficacy.
Objectives: To assess the beneficial effects and harms of Chinese herbal medicine for people with diabetic peripheral neuropathy.
Search strategy: We searched the Cochrane Neuromuscular Disease Group Specialized Register (15 June 2010), the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 2, 2010 in The Cochrane Library), MEDLINE (January 1966 to June 2010), EMBASE (January 1980 to June 2010), AMED (January 1985 to June 2010), Chinese Biomedical Database (CBM) (1979 to June 2010), Chinese National Knowledge Infrastructure Database (CNKI) (1979 to June 2010), and VIP Chinese Science and Technique Journals Database (1989 to June 2010). We searched for unpublished literature in the Chinese Conference Papers Database and Chinese Dissertation Database (from inception to March 2010). No language or publication restrictions were used.
Selection criteria: We included randomized controlled trials of Chinese herbal medicine (with a minimum of four weeks treatment duration) for people with diabetic peripheral neuropathy compared with placebo, no intervention, or conventional interventions. Trials of herbal medicine plus a conventional drug versus the drug alone were also included.
Data collection and analysis: Two authors independently extracted data and evaluated trial quality. We contacted study authors for additional information. The data analyses were carried out using Review Manager 5.1 (Cochrane software).
Main results: Thirty-nine randomized trials involving 2890 participants were included. All trials were conducted and published in China. Thirty different herbal medicines were tested in these trials, including four single herbs (extracts from a single herb), eight traditional Chinese patent medicines, and 18 self-concocted Chinese herbal compound prescriptions. The trials reported on global symptom improvement (including improvement in numbness or pain) and changes in nerve conduction velocity. There was inadequate reporting on adverse events in the included trials. Most of the trials did not mention whether they monitored adverse effects at all. Only two trials reported adverse events: one occurred in the control group in one trial and in which group was unclear in the other trial . Conclusions cannot be drawn from this review about the safety of herbal medicines due to inadequate reporting. Most of the trials were of low methodological quality and therefore the interpretation of any positive findings for the efficacy of the included Chinese herbal medicines for treating diabetic peripheral neuropathy should be made with caution.
Authors' conclusions: Based on this systematic review, there is no evidence to support the objective effectiveness and safety of Chinese herbal medicines for diabetic peripheral neuropathy. No well designed, randomized placebo controlled trial with objective outcome measures has been conducted.