Acute Lower Back Problems in Adults - Muscle Relaxants

Muscle Relaxants

Panel findings and recommendations:

• Muscle relaxants are an option in the treatment of patients with acute low back problems. While probably more effective than placebo, muscle relaxants have not been shown to be more effective than NSAIDs. (Strength of Evidence = C.)
  
• No additional benefit is gained by using muscle relaxants in combination with NSAIDs over using NSAIDs alone. (Strength of Evidence = C.)
  
• Muscle relaxants have potential side effects, including drowsiness in up to 30 percent of patients. When considering the optional use of muscle relaxants, the clinician should balance the potential for drowsiness against a patient's intolerance of other agents. (Strength of Evidence = C.)

Muscle relaxants are commonly used for the treatment of low back problems. Pharmacologically, these are usually benzodiazepines, other sedative medications, or antihistamine derivatives. The therapeutic objective of muscle relaxants is to reduce low back pain by relieving muscle spasm. However, the concept of skeletal muscle spasm is not universally accepted as a cause of symptoms, and the most commonly used muscle relaxants have no peripheral effect on muscle spasm.

Literature Reviewed.

Of 42 articles screened for this topic, 12 RCTs met review criteria for adequate evidence about efficacy. [91, <http://text.nlm.nih.gov> [104 <http://text.nlm.nih.gov>– 114] <http://text.nlm.nih.gov>

Evidence on Efficacy.

Three studies evaluating patients with low back problems either did not specify duration of symptoms or included a mix of patients with acute and chronic problems. [104, <http://text.nlm.nih.gov> 113, <http://text.nlm.nih.gov> 114] <http://text.nlm.nih.gov> The remaining nine studies evaluated only patients with acute low back problems.

Of the articles that met review criteria, 9 evaluated a muscle relaxant compared with a placebo. [91, <http://text.nlm.nih.gov> 104, <http://text.nlm.nih.gov> 105, <http://text.nlm.nih.gov> 108– <http://text.nlm.nih.gov> 113] <http://text.nlm.nih.gov> Two studies compared two different muscle relaxants. [107] <http://text.nlm.nih.gov>, [114] <http://text.nlm.nih.gov> Some of the studies also compared a muscle relaxant to another medication, including a barbiturate; [110] <http://text.nlm.nih.gov>, [111] <http://text.nlm.nih.gov> an NSAID; [91] <http://text.nlm.nih.gov>, [106] <http://text.nlm.nih.gov>and acetaminophen. [91] <http://text.nlm.nih.gov>

Of the nine studies comparing muscle relaxants with placebos, seven had results favoring the muscle relaxant. [104] <http://text.nlm.nih.gov>, [105] <http://text.nlm.nih.gov>, [108] <http://text.nlm.nih.gov> – [111] <http://text.nlm.nih.gov>, [113] <http://text.nlm.nih.gov> Two showed no difference in outcomes between muscle relaxant and placebo. [91] <http://text.nlm.nih.gov>, [112] <http://text.nlm.nih.gov> In most studies, the positive effect for muscle relaxants was short–lived, lasting no more than 4 to 7 days, with no significant difference from placebo seen after this time.

Panel methodologists did a meta–analysis of the 12 studies that met panel review criteria. The studies were assessed for quality without knowledge of the results. There was one excellent study, [107] <http://text.nlm.nih.gov> three good studies, [105] <http://text.nlm.nih.gov>, [109] <http://text.nlm.nih.gov>, [114] <http://text.nlm.nih.gov> and eight fair studies. [91] <http://text.nlm.nih.gov>, [104] <http://text.nlm.nih.gov>, [106] <http://text.nlm.nih.gov>, [108] <http://text.nlm.nih.gov>, [110] <http://text.nlm.nih.gov> – [113] <http://text.nlm.nih.gov>

Each study was examined for outcome measures such as pain, functional capacity, or a global measure of improvement. When meta–analytically combined, the studies showed a trend toward greater improvement in the patients treated with muscle relaxants, but did not reach statistical significance. Even if the findings had reached significance, statistical combinations of such study results should be interpreted with caution. The conclusion of the meta–analysis was that muscle relaxants are probably, but not certainly, more effective than placebos in decreasing symptoms of acute low back problems. However, there was not enough evidence to determine whether muscle relaxants are more or less effective than NSAIDs for reducing symptoms or whether the addition of a muscle relaxant adds to the efficacy of an NSAID.

Potential Harms and Costs.

Potential complications of muscle relaxants include drowsiness and dizziness, reported to be up to 30 percent higher in patients taking muscle relaxants compared with patients taking placebos. [91] <http://text.nlm.nih.gov>, [104] <http://text.nlm.nih.gov>, [105] <http://text.nlm.nih.gov>, [108] <http://text.nlm.nih.gov> – [113] <http://text.nlm.nih.gov> The cost of muscle relaxants is considered low to moderate.

Summary of Findings.

There is moderate research evidence that muscle relaxants are more effective than placebo, but no evidence that they are better than NSAIDs, in relieving symptoms of acute low back problems. These medications have substantial potential side effects, especially a high incidence of drowsiness.
Opioid Analgesics

Panel findings and recommendations:

• When used only for a time–limited course, opioid analgesics are an option in the management of patients with acute low back problems. The decision to use opioids should be guided by consideration of their potential complications relative to other options. (Strength of Evidence = C.)
  
• Opioids appear to be no more effective in relieving low back symptoms than safer analgesics, such as acetaminophen or aspirin or other NSAIDs. (Strength of Evidence = C.)
  
• Clinicians should be aware of the side effects of opioids, such as decreased reaction time, clouded judgment, and drowsiness, which lead to early discontinuation by as many as 35 percent of patients. (Strength of Evidence = C.)
  
• Patients should be warned about potential physical dependence and the danger associated with the use of opioids while operating heavy equipment or driving. (Strength of Evidence = C.)

Oral opioid analgesics commonly given to patients with acute low back problems include morphine derivatives (opioids) and synthetic opioids. The therapeutic objective in treating low back problems is temporary pain relief.

Literature Reviewed.

No RCTs were found that compared opioid analgesics (either alone or in combination with other drugs) to a placebo. Therefore, three studies were evaluated that compared opioid analgesics to other medications, [115] <http://text.nlm.nih.gov> – [117] <http://text.nlm.nih.gov> recognizing that results of the evaluation would not entirely answer the question of whether opioids are any better than placebo for back symptoms. Another article [118] <http://text.nlm.nih.gov> contained information used by the panel.

Evidence on Efficacy.

All three studies evaluated patients with acute low back problems, but with a mixed group of medications. Two reports compared acetaminophen with codeine to diflunisal (an NSAID) with patients treated for 1 and 2 weeks, respectively. [115] <http://text.nlm.nih.gov>, [116] <http://text.nlm.nih.gov> The third study compared three groups, one group receiving codeine, one oxycodone plus aspirin, and one acetaminophen. [117] <http://text.nlm.nih.gov>

At the conclusion of treatment, Muncie, King, and DeForge [116] <http://text.nlm.nih.gov> and Brown, Bodison, Dixon, et al. [115] <http://text.nlm.nih.gov> found no significant differences between groups in terms of pain relief or functional improvement.
Wiesel, Cuckler, Deluca, et al., [117] <http://text.nlm.nih.gov> who evaluated a population of military recruits with acute low back pain, found no difference between the three medication groups in amount of time before patients returned to full activities. Pain relief was claimed to be superior in groups receiving opioid analgesics compared with acetaminophen, with the greatest effect seen in the first 3 days of treatment. No statistics were reported to support the claim.

Potential Harms and Costs.

Side effects reported by subjects receiving acetaminophen with codeine included dizziness, fatigue, inability to concentrate, impaired vision, drowsiness, nausea, and constipation. [115] <http://text.nlm.nih.gov>, [116] <http://text.nlm.nih.gov> In one study, 35 percent of subjects receiving acetaminophen with codeine had to discontinue the medication because of intolerable side effects. [116] <http://text.nlm.nih.gov> Prolonged use of opioid analgesics is associated with the development of tolerance and physical dependence. A risk of developing physical dependence with short–term use of opioids has also been reported. [118] <http://text.nlm.nih.gov>
The expense of treatment with these medications varies greatly, depending on the medication used and the length of treatment.

Summary of Findings.

There are no well–designed controlled studies that evaluate the use of opioid analgesics compared with no treatment in patients with acute low back problems. The studies reviewed found that patients taking opioid analgesics did not return to full activity sooner than patients taking NSAIDs or acetaminophen. In addition, two studies found no difference in pain relief between NSAIDs and opioids. Finally, side effects of opioid analgesics were found to be substantial, including the risk for physical dependence. These side effects are an important concern in conditions that can become chronic, such as low back problems.


Bigos S, Bowyer O, Braen G, et al. Acute Low Back Problems in Adults.
Clinical Practice Guideline No. 14. AHCPR Publication No. 95–0642.
Rockville, MD: Agency for Health Care Policy and Research, Public Health
Service, U.S. Department of Health and Human Services. December 1994.