Metformin for low back pain: Study protocol for a randomised, double-blind, placebo-controlled trial

Background: Chronic low back pain is a major cause of pain and disability with limited effective therapies. Metformin is a safe, inexpensive, well-tolerated drug that has pleotropic effects, including effects on pain pathways that may influence low back pain. The aim of this randomised, double-blind, placebo-controlled trial is to determine whether metformin reduces low back pain over 4 months in individuals with chronic low back pain. Methods and analysis: One hundred and twenty-three participants with chronic low back pain will be recruited from the community in Melbourne, Australia, and randomly allocated in a 1:1 ratio to receive either metformin 2g or identical placebo daily for 4 months. The primary outcome will be change in pain intensity assessed using a 100 ​mm visual analogue scale at 4 months and the secondary outcomes will be change in low back disability, physical activity and narcotic use. Adverse events will be recorded. The primary analysis will be by intention to treat. Discussion: Given the societal burden of LBP and the limited effective treatment options available, this study that evaluates the efficacy of metformin in LBP, if proves to be effective, will offer an important therapeutic approach for this disabling condition. Ethics and dissemination: Ethics approval has been obtained from the Alfred Hospital Ethics Committee (392/21) and Monash University Human Research Ethics Committee (30607). Written informed consent will be obtained from all the participants. The findings will be disseminated through peer-review publications and conference presentations. Trial registration: Australian New Zealand Clinical Trials Registry, ACTRN12621001453875 (registered 25th October 2021).