Effect of topical Zingiber cassumunar on painful diabetic neuropathy: a double-blind randomized-controlled trial [version 2; peer review: 1 approved]

Background Plai or Zingiber cassumunar Roxb. was registered into the Thai Traditional Medicine list since 2011. However, there is limited evidence regarding Plai as a treatment in painful diabetic neuropathy (PDN). Therefore, this study aimed to evaluate the efficacy of topical Zingiber cassumunar. Methods A RCT was conducted in patients with PDN during February to March 2019. All participants received oral gabapentin 300 mg before bed as a standard regimen. The intervention group (n=16) received Plai balm 15%w/w 0.5 gram to apply on their feet three times a day and the control group (n=15) received placebo balm to similarly apply. Pain score at baseline, 2 nd and 4 th weeks were assessed and compared. Patients’ quality of life, and adverse events, were collected. Mean pain scores before and after treatment in each group and between groups were also analyzed. Results At the end of week two and week four, the Plai group showed statistically significant lesser mean pain scores than the placebo group by -1.47 (95%CI: -1.96 to -1.30, p-value < 0.001), and by -1.51 (95%CI: -1.92 to -0.13, p-value = 0.027), respectively. Moreover, the Plai group had more cases number/ percentages with at least 50% pain score reduction than the placebo group [12/16 (75%) vs 3/15 (20%), p-value = 0.004]. However, there was no statistically significant difference in quality of life between the two groups (overall p-value = 0.366). Adverse event was not found in any groups. Conclusions Zingiber cassumunar balm (Plai) was efficacious for pain reduction in painful diabetic neuropathy. Registration Registered with the Thai Clinical Trials Registry; TCTR20200221001.