Chinese herbal medicine for treatment of diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is one of the most common complications of diabetes. It is characterised by a progressive loss of nerve fibres that predisposes the person to painful or insensitive extremities, ulceration and amputation, and results in a large disease burden in terms of incapacity for work, quality of life and use of healthcare resources. This systematic review identified a total of 49 trials that included 3639 participants with DPN. Ten of the trials were new at this first update of the review. We evaluated the effects of various herbal formulations (including single herbs, Chinese proprietary medicines and mixtures of different herbs) for treating people with DPN. All the identified clinical trials were performed and published in China. The trials reported on global symptom improvement (including improvement in numbness or pain) and changes in nerve conduction velocity. The positive results described from the 49 studies of low quality are of questionable significance. There was inadequate reporting on adverse events in the included trials. Most of the trials did not mention whether they monitored for adverse effects. Only two trials reported adverse events but an adverse event occurred in the control group in one trial and it was unclear in which group they occurred in the other trial. Conclusions about the safety of herbal medicines cannot therefore be drawn from this review due to inadequate reporting. Most of the trials were of very low methodological quality and the interpretation of any positive findings for the efficacy of the included Chinese herbal medicines for treating DPN should be made with caution. Based on this systematic review, there is no evidence to support the objective effectiveness and safety of Chinese herbal medicines for DPN. No well-designed, randomised placebo controlled trial with objective outcome measures has been conducted.

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, randomised, placebo controlled trial with objective outcome measures has been conducted.

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Background: 

Chinese herbal medicine is frequently used for treating diabetic peripheral neuropathy in China. Many controlled trials have been undertaken to investigate its efficacy.

This is an update of a Cochrane review that was first published in the year 2011.

Objectives: 

To assess the beneficial effects and harms of Chinese herbal medicine for people with diabetic peripheral neuropathy.

Search strategy: 

On 14 May 2012, we searched the Cochrane Neuromuscular Disease Group Specialized Register CENTRAL (2012, Issue 4 in The Cochrane Library), MEDLINE (January 1966 to May 2012), EMBASE (January 1980 to May 2012), AMED (January 1985 to May 2012) and in October 2012, the Chinese Biomedical Database (CBM) (1979 to October 2012), Chinese National Knowledge Infrastructure Database (CNKI) (1979 to October 2012), and VIP Chinese Science and Technique Journals Database (1989 to October 2012). We searched for unpublished literature in the Chinese Conference Papers Database, and Chinese Dissertation Database (from inception to October 2012). There were no language or publication restrictions.

Selection criteria: 

We included randomised 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.

Main results: 

Forty-nine randomised trials involving 3639 participants were included. All trials were conducted and published in China. Thirty-eight different herbal medicines were tested in these trials, including four single herbs (extracts from a single herb), eight traditional Chinese patent medicines, and 26 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. The positive results described from the 49 studies of low quality are of questionable significance. There was inadequate reporting on adverse events in the included trials. Eighteen trials found no adverse events. Two trials reported adverse events: adverse events occurred in the control group in one trial, and in the other it was unclear in which group the adverse events occurred. 29 trials did not mention whether they monitored adverse events. Conclusions cannot be drawn from this review about the safety of herbal medicines, due to inadequate reporting. Most of the trials were of very 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.

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