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Muscle relaxants for acute low back pain

Three Part Question

[In patients with simple acute low back pain] are [muscle relaxants better than placebo] at [decreasing pain, improving mobility and speeding a return to normal activities (e.g. work)]

Clinical Scenario

A 35 year old woman presents to the emergency department with acute lower back pain radiating to her right buttock. Neurological examination is normal and there are no "red flag" symptoms or signs to suggest that this is anything other than simple low back pain. You treat her with oral paracetamol and voltarol and return to review her later. She is still in pain and appears to get a lot of spasm when she tries to get up. You suggest a course of diazepam to act as a muscle relaxant but your registrar says that it is a waste of time and to get her going quick as it is 3 hours since she arrived in the department.

Search Strategy

[muscle relaxant$ or exp muscle relaxants, central/ or or or exp.BENZODIAZEPINES or or exp Parasympatholytics/] and [back or exp back pain/ or exp low back pain or lumbar]
OVID Medline on the www. via ATHENS 1966-2005

Search Outcome

One high quality systematic review was found from 2003 which searched up until October 2001. The Medline search was therefore restricted to after October 2001 to identify anuy new papers not in the systematic review.
Medline: 57 papers were found of which 3 were relevant to the clinical question

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
van Tulder
Review of papers examining the use of muscle relaxants in patients with simple low back pain. Only RCTs and CCTs were included in the article.Systematic reviewBenzodiazepine vs placebo in acute back painOne low quality trial. Benefit in use of benzodiazepines.This is a well conducted review article. There is also a Cochrane review by the same authors on the same subject. The outcomes in individual trials are often disparate making grouping of results difficult.
Nonbenzodiazepines vs placebo in acute back pain4 trials (3 high quality, 1 low quality) showed benefit to muscle relaxants in short term pain relief , global efficiency and physical outcome.
Side effects in acute lower back painAll trials showed clinically and statistically significant increases in side effects of muscle relaxants (e.g. drowsiness, dizziness)
Antispasticity drugs for acute low back pain2 high quality trials both demonstrated a benefit in acute low back pain
Muscle relaxants + analgesics/NSAIDS vs. placebo + analgesics/NSAIDS in acute back pain3 trials. Benefit in use of muscle relaxants but a significant increase in side effect reporting.
Injection therapyStrong evidence of benefit in acute back pain
Bernstein et al
1633 patients with low back pain. Recruited from community practitioners. Observed to determine if the use of muscle relaxants was associated with a more rapid recovery. No interventions were made by the authors on the care of the patients.Observational cohort.Baseline data on patient mix24% had sciatica. average pain was 5.4 on a 10 point scale. Average Roland baseline score was 11.2. Mean time to functional recovery (if recovered) was 16.2 days.Only looked at time to return to normal function. benefit in treatment may be in relief of symptoms only which would be missed on this study. Purely observational study which is prone to a great deal of bias. Groups clearly different at baseline with users of muscle relaxants apparently having a greater degree of illness (though this is adjusted for in the Cox analysis)
Use of muscle relaxants49% of patients used muscle relaxants
Statistically significant differences in patient characteristics between users and non usersUsers were on average 2.3 years younger (p=0.012); female 50% vs 45%; on workers compensation 34% vs 28%; or if they had a higher pain score, roland disability score or if they took longer to recover. They were less likely to be used if the patient had seen a chiropracter as initial provide 18% vs 55%;
Time to achieve functional recovery on Cox proportional hazards model.No difference in recovery rates between those using muscle relaxants and those not.
Hoiriis et al
192 patients with back pain of 2-6 weeks duration. Randomised to either chiropractic plus placebo, relaxant plus sham chiro or sham both. Followed up for 4 weeks.PRCTVAS for painAll groups reduced significantly. No statistical difference between groups.Difficult to produce a sham chiropractic but the authors have tried hard to do so in this study.
Oswestry disability indexAll groups reduced significantly. No statistical difference between groups.
Modified ZungAll groups reduced significantly. No statistical difference between groups.
Schobers testNo group significantly improved flexibility. No statistical difference between groups.


Acute back pain is a common problem in emergency medicine and general practice. Whilst the majority of patients seem to cope well with advice and simple analgesics many complain of spasmodic pain and stiffness. There therefore appears to be a logical argument for the use of muscle relaxants. This is supported by the papers in the table. The systematic review demonstrates that in RCTs and CCTs there does appear to be a real benefit from the use of muscle relaxants in the acute and chronic settings. However, the incidence of side effects is considerable and thei blanket use cannot be advocated. It will remain up to the treating physician to assess the need for and the potential risks in individual patients

Clinical Bottom Line

Muscle relaxants are effective in the management of acute and chronic back pain. However, the incidence of side effects means that they must be used with caution.

Level of Evidence

Level 1 - Recent well-done systematic review was considered or a study of high quality is available.


  1. van Tulder MW, Touray T, Furlan AD, Solway S, Bouter LM. Muscle relaxants for nonspecific low back pain: A systematic review within the framework of the Cochrane Collaboration Spine 2003;28:1978-1992
  2. Bernstein E, Carey TS, Garrett JM. The use of muscle relaxant medication in acute low back pain Spine 2004;29:1346-1351
  3. Hoiriis KT, Pfleger B, McDuffie C, Cotsonis MA, Elsangak O, Hinson R, Verzosa GT. A randomized clinical trial comparing chiropractic adjustments to muscle relaxants for subacute low back pain. Journal of manipulative and physiological therapeutics 2004;27:388-398