What is the role of muscle relaxants in the management of low back pain (LBP) and sciatica?

Updated: Aug 22, 2018
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
  • Print


Muscle spasmolytics or relaxants are traditionally used to treat painful musculoskeletal disorders. As a class, they have demonstrated more CNS side effects than a placebo, sharing sedation and dizziness as common side effects. Therefore, patients should be cautioned about these side effects and weigh them against the potential benefits. [59, 61, 66, 63] A recently published review and analysis of randomized or double-blinded controlled trials showed that muscle relaxants were effective for the management of LBP, but adverse side effects limited their use. [66] With some patients, these medications can only be considered for use at bedtime. Some muscle spasmolytics are also potentially addictive and have abuse potential, especially more traditional agents such as diazepam, butalbital, and phenobarbital.

The category of muscle relaxants includes a heterogeneous group of medications that some experts divide into benzodiazepines and nonbenzodiazepines. Benzodiazepines may be appropriate for concurrent anxiety states, and in those cases, clonazepam should be considered for its clinical use. Clonazepam is a benzodiazepine that operates via GABA-mediated mechanisms through the internuncial neurons of the spinal cord to provide muscle relaxation. [67] Strong evidence shows that another benzodiazepine, tetrazepam, is more effective than a placebo at treating short-term pain and some indicate that it also improves muscle spasms; however, data on long-term outcomes are inadequate. [59]

The data on nonbenzodiazepine muscle relaxants are not as strong, but moderate evidence exists for short-term overall improvements, although little or no improvement has been shown in specific pain outcomes. [66]

Examples of commonly used nonbenzodiazepine muscle relaxants include cyclobenzaprine, carisoprodol, methocarbamol, chlorzoxazone, and metaxalone. A comprehensive evaluation and meta-analysis of cyclobenzaprine’s effectiveness showed support for short-term use (< 4 d) with a modest benefit early in LBP treatment, but with the same problematic side effects. [68]

Tizanidine is a central α-2 adrenoreceptor agonist that was developed for the management of spasticity due to cerebral or spinal cord injury, but also has demonstrated efficacy when compared to other muscle spasmolytics. [69] The muscle spasmolytic effects of tizanidine are thought to relate primarily to centrally acting α2-adrenergic activity at both the spinal cord and supraspinal levels. [70] Several clinical trials have demonstrated the efficacy of tizanidine for the treatment of acute neck and back pain. [71, 72, 73, 74, 75] Controlled studies have demonstrated reduced analgesic use and muscle spasm in patients with acute neck and back pain. [73]

Specifically, comparison studies have shown that tizanidine is as effective as diazepam and chlorzoxazone for treatment of these acute conditions. [74] Tizanidine exerts no significant effect on muscle tone, so patients report muscle weakness less often as a side effect than with diazepam or other muscle relaxants. [75] The onset of action of tizanidine is rapid with peak plasma concentrations occurring at 1-2 hours following oral administration. [75] The elimination half-life of tizanidine is approximately 2.5 hours with significant interpatient variability. [75]

This rapid onset of action coupled with its muscle spasmolytic and antinociceptive properties has spurred investigation into clinical use not only for the treatment of acute spinal pain with muscle spasm, but also as therapy for other painful chronic muscular conditions.

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!