Skeletal muscle relaxants are widely used in treating musculoskeletal conditions. However, evidence of their effectiveness consists mainly of studies with poor methodologic design. In addition, these drugs have not been proven to be superior to
acetaminophen or nonsteroidal anti-inflammatory drugs for
low back pain. Systematic reviews and meta-analyses support using
skeletal muscle relaxants for short-term relief of acute
low back pain when nonsteroidal anti-inflammatory drugs or
acetaminophen are not effective or tolerated. Comparison studies have not shown one skeletal muscle relaxant to be superior to another.
Cyclobenzaprine is the most heavily studied and has been shown to be effective for various musculoskeletal conditions. The
sedative properties of
tizanidine and
cyclobenzaprine may benefit patients with
insomnia caused by severe
muscle spasms.
Methocarbamol and
metaxalone are less sedating, although effectiveness evidence is limited. Adverse effects, particularly
dizziness and drowsiness, are consistently reported with all
skeletal muscle relaxants. The potential adverse effects should be communicated clearly to the patient. Because of limited comparable effectiveness data, choice of agent should be based on side-effect profile, patient preference, abuse potential, and possible drug interactions.