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Methocarbamol versus diazepam in acute low back pain in the emergency department: a randomised double-blind clinical trial
  1. Meisam Sharifi1,
  2. Ali Abdorazzaghnejad2,
  3. Mahtab Yazdchi1,
  4. Maryam Bahreini3,4
  1. 1Department of Emergency Medicine, Tehran University of Medical Sciences, Tehran, Iran
  2. 2Department of Emergency Medicine, Zahedan University of Medical Sciences, Zahedan, Iran
  3. 3Emergency Medicine, Tehran University of Medical Sciences, Tehran, Iran
  4. 4Faculty of Medicine and Health Sciences, McGill University, Montreal, Québec, Canada
  1. Correspondence to Dr Maryam Bahreini, Emergency Medicine, Tehran University of Medical Sciences, Tehran, Iran; bahreinimaryam{at}


Background Acute low back pain (LBP) is a common complaint in the emergency department and achieving effective analgesia can be challenging.

Methods In this multicentre randomised double-blind clinical trial conducted at three EDs in Iran from August to November 2020, we assessed the efficacy and adverse effects of two muscle relaxants in patients aged 18 years or older who suffered LBP in the last 6 weeks. Group 1 received intravenous methocarbamol and group 2 received intravenous diazepam followed by a weight-based dose of intravenous morphine in both groups. Exclusion criteria mainly included non-spine aetiologies, cord compression, acute gastrointestinal bleeding, renal/hepatic insufficiency, pregnancy, breast feeding and unstable vital signs. Pain scores and adverse events were measured by a Numeric Rating Scale (NRS) at baseline and after 30 and 60 min by one of the researchers who was not involved with patient visits and was blinded to the intervention. We used t-test to assess the mean difference of NRS at 30 and 60 min.

Results Out of 101 enrolled patients, 50 participants received methocarbamol and 51 diazepam. The baseline mean pain scores and demographic characteristics were not different between the study groups. Pain scores were reduced by both agents after 60 min, with slightly greater pain reductions in the diazepam group in comparison with methocarbamol (mean difference −6.1, 95% CI −6.5 to −5.7 vs mean difference −5.2, 95% CI –5.7 to −4.7, respectively, p<0.001). ED length of stay of patients did not differ between the groups (methocarbamol 5.9 vs diazepam 4.8 hours, p=0.365). Patients receiving diazepam were more likely to report drowsiness (2 (4.0%) vs 15 (29.4%), p=0.001).

Conclusions In patients with LBP, the pain was relieved in the methocarbamol and diazepam groups after 60 min. Although diazepam was more effective, its use was associated with a slightly higher risk of drowsiness.

Trial registration number The protocol of this clinical trial was prospectively registered in the (IRCTID: IRCT20151113025025N4; .

  • ED
  • acute care
  • analgesia
  • assessment

Data availability statement

Data are available on reasonable request.

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Data availability statement

Data are available on reasonable request.

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  • Handling editor David Metcalfe

  • Contributors The guarantors, AA, MB, MY and MS conceived the study, designed it and supervised the conduct of the study and collected data. MB, AA, MY and MS undertook recruitment of participants and managed the data, including quality control. MB, MS and AA provided statistical advice on study design and analysed the data; MB, AA, MS and MY drafted the manuscript, and all the authors contributed substantially to its revision and all take responsibility for the paper as a whole.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, conduct, reporting or dissemination plans of this research.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.