The efficacy of methylene blue for back pain: a meta-analysis of randomized controlled trials

Introduction: The efficacy of methylene blue for back pain remains controversial. We conduct a systematic review and meta-analysis to explore the impact of methylene blue versus placebo on back pain. Methods: We searched PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through June 2018 for randomized controlled trials (RCTs) assessing the effect of methylene blue versus placebo on the alleviation of back pain. This meta-analysis is performed using the random-effect model. Results: Three RCTs involving 229 patients are included in the meta-analysis. Overall, compared with control group for back pain, methylene blue can remarkably decrease pain scores at 24-48 h (Std. MD = -1.69; 95% CI = -2.07 to -1.32; P < 0.00001), 2-3 month (Std. MD = -1.09; 95% CI = -1.62 to -0.56; P < 0.0001), and ODI at 2-3 month (Std. MD = -0.85; 95% CI = -1.18 to -0.52; P < 0.00001), as well as moderate-severe functional disability after 3-6 months (RR = 0.46; 95% CI = 0.24 to 0.87; P = 0.02), but has no significant impact on pain scores (Std. MD = -1.60; 95% CI = -3.50 to 0.30; P = 0.10) and ODI (Std. MD = -1.95; 95% CI = -4.34 to 0.44; P = 0.11) at 6 months. Conclusions: Methylene blue can substantially decrease pain scores and ODI within 3 months, as well as moderate-severe functional disability after 3-6 months in patients with back pain.