Topical Herbal Medicine for Treatment of Diabetic Peripheral Neuropathy: A Systematic Review of Randomized Controlled Trials

Background: Topical Chinese herbal medicine (CHM) is generally used in China, separately or in combination with conventional medicine, to treat diabetic peripheral neuropathy (DPN). Clinical studies have shown beneficial effects of CHM compared with conventional medicine. Material and Methods: A systematic literature search of Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, AMED, Chinese BioMedical Literature Database (CBM), Chinese National Knowledge Infrastructure (CNKI) and Chinese Scientific Journal Database (VIP) information was conducted till March 2010. Randomized controlled trials (RCTs) were included if they compared topical CHM to conventional medicine, placebo or no treatment for patients with DPN. Revman 5.0.17 was used as software for data analysis. The effect expectancy is depicted as relative risk and mean difference with a 95% confidence interval. Results: 23 RCTs including 22 topical CHMs were included. The methodological quality of the included trials is generally poor in terms of sequence generation, concealment of allocations, blinding, incomplete data outcome and selective outcome reports. 17 trials showed beneficial effects of CHM on global symptom improvement, 6 beneficial effects of CHM on nerve velocity conduction, 4 beneficial effects of CHM on numbness improvement and 4 beneficial effects of CHM on pain relief. Adverse events with relation to CHM were reported in 3 trials including skin redness, a burning feeling, a prickling sensation and rash. Conclusions: Due to weak evidence, the claimed benefits of topical CHM for DPN are inconclusive; more stringent studies are needed to support clinical practice.