In general, all of the drugs were shown to have some benefit.18 The limitations of published comparison trials include using unvalidated scales to measure outcomes, involving small numbers of participants, and often not reporting adverse effects of studied medications. Cyclobenzaprine hydrochloride effect on skeletal muscle spasm in the lumbar region and neck: two double-blind controlled clinical laboratory studies. One fair-quality study showed carisoprodol was better than diazepam at improving muscle spasm and global and functional status in patients with low back pain.30 Another fair-quality study comparing tizanidine with chlorzoxazone (Parafon Forte) for back spasms did not show any significant difference.31A different systematic review did include some studies which were considered to be high quality.17 These studies revealed no difference in outcomes (e.g., muscle spasms, muscle pain, tension, tenderness, functional status) among cyclobenzaprine versus carisoprodol; chlorzoxa-zone versus tizanidine; or diazepam versus tizanidine.17Although the evidence for effectiveness of skeletal muscle relaxants in musculoskeletal conditions is limited, strong evidence does exist in terms of toxicity. One fair-quality study showed no difference between metaxalone and placebo.19 Limited evidence exists to support the use of skeletal muscle relaxants in chronic low back pain.1720 Benzodiazepines have been effective for short-term use compared with placebo, but the basis of this recommendation stemmed from trials involving tetrazepam, which is not available in the United States.2126 One meta-analysis evaluated 14 studies comparing cyclobenzaprine with placebo for back and neck pain.27 The trials included were of less than 14 days' duration.Cyclobenzaprine was found to be moderately more effective than placebo, but had more central nervous system adverse effects.Skeletal muscle relaxants are widely used in treating musculoskeletal conditions.
Methocarbamol and metaxalone are less sedating, although effectiveness evidence is limited.
Similar recommendations exist in treating tension headaches.13 A meta-analysis evaluating the use of cyclobenzaprine showed that, although this drug was better than placebo for the treatment of fibromyalgia, it was considered inferior to antidepressants.14 Additionally, recent guidelines on fibromyalgia recommend using a comprehensive approach that utilizes tramadol (Ultram), antidepressants, and/or a heated pool (with or without exercise).15Prescription rates for nonspecific back pain revealed that skeletal muscle relaxants accounted for 18.5 percent of prescriptions compared with 16.3 percent for NSAIDs and 10 percent for cyclooxygenase-2 inhibitors.16 Because of the high rate of prescribing skeletal muscle relaxants, an understanding of the risks and benefits of this class of drugs is vital.
This article presents evidence regarding the use of antispasmodic skeletal muscle relaxants for various musculoskeletal conditions, and appropriate drug selection if a skeletal muscle relaxant is required.
Antispastic agents (e.g., baclofen [Lioresal], dantrolene [Dantrium]) should not be prescribed for musculoskeletal conditions because there is sparse evidence to support their use.
Rather, an antispasmodic agent may be more appropriate Allergy-type reactions may occur after the first to fourth dose; may be mild (e.g., cutaneous rash) or more severe (e.g., asthma attack, angioneurotic edema, hypotension, or anaphylactic shock); antihistamines, epinephrine, or corticosteroids may be needed The table contains only selected highlights about these medications.