DRUGS USED TO TREAT ACUTE LOCAL
A large number of less well-studied, centrally active drugs (eg,
chlorzoxazone, cycloben-zaprine, metaxalone, methocarbamol, and orphenadrine)are promoted for the
relief of acute muscle spasm caused by local tissue trauma or muscle strains.
It has been suggested that these drugs act primarily at the level of the
brainstem. Cyclobenzaprine may be regarded as the prototype of the group.
Cyclobenzaprine is structurally related to the tricyclic antidepressants and
produces antimuscarinic side effects. It is ineffective in treating muscle
spasm due to cerebral palsy or spinal cord injury. As a result of its strong
antimuscarinic actions, cyclobenzaprine may cause significant sedation, as well
as confusion and transient visual hallucinations. The dosage of cyclobenzaprine
for acute injury-related muscle spasm is 20–40 mg/d orally in divided doses.