A Systematic Review and Meta-Analysis of Efficacy of Botulinum Toxin A for Neuropathic Pain

We performed a systematic review and meta-analysis of randomised controlled trials (RCTs) conducted from January 2005 to June 2021 to update the evidence of Botulinum toxin A (BoNT-A) in neuropathic pain (NP) in addition to quality of life (QOL), mental health, and sleep outcomes. We conducted a Cochrane Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria analysis of RCTs from the following data sources: EMBASE, CINAHL, WHO International Clinical Trial Registry Platform, ClinicalTrials.gov, Cochrane database, Cochrane Clinical Trial Register, Australia New Zealand Clinical Trials Registry, and EU Clinical Trials Register. Meta-analysis of 17 studies showed a mean final VAS reduction in pain in the intervention group of 2.59 units (95% confidence interval: 1.79, 3.38) greater than the mean for the placebo group. The overall mean difference for sleep, Hospital Anxiety and Depression Scale (HADS) anxiety, HADS depression, and QOL mental and physical sub-scales were, respectively, 1.10 (95% CI: -1.71, 3.90), 1.41 (95% CI: -0.61, 3.43), -0.16 (95% CI: -1.95, 1.63), 0.85 (95% CI: -1.85, 3.56), and -0.71 (95% CI: -3.39, 1.97), indicating no significance. BoNT-A is effective for NP; however, small-scale RCTs to date have been limited in evidence. The reasons for this are discussed, and methods for future RCTs are developed to establish BoNT-A as the first-line agent.