7.13 : Centrally Acting Muscle Relaxants: Therapeutic Uses

Centrally acting muscle relaxants act on different receptors of pre and postsynaptic neurons in the central nervous system to reduce muscle tone and tension.

Based on their therapeutic use, centrally acting muscle relaxants are classified into spasmolytic and antispasmodic drugs.

Spasmolytic drugs inhibit spinal motor neurons and decrease muscle tone. Some spasmolytics like baclofen and diazepam, are γ-aminobutyric acid agonists, whereas tizanidine is an ɑ-2-adrenoceptor agonist.

These drugs treat severe and chronic muscle spasms caused by stroke, cerebral palsy, spinal cord and muscle injuries, and multiple sclerosis. If withdrawn abruptly, these drugs can have side effects like sedation, weakness, and return of spasticity.

In contrast, antispasmodic drugs such as cyclobenzaprine, methocarbamol, and orphenadrine primarily act on the brain stem and reduce hyperactive muscle reflexes.

They treat acute muscle spasms caused by local muscle injury, trauma and inflammation. Their side effects include visual hallucinations, constipation and urinary retention.