Definition of Centrally Acting Muscle Relaxants:
- Centrally acting muscle relaxants are a class of drugs that reduce muscle tone and help relieve muscle spasms through actions on the central nervous system (CNS) rather than directly on skeletal muscles.
Mechanism of Action:
- These drugs work primarily by:
- Depressing neuronal activity in the brain and/or spinal cord.
- They often enhance inhibitory pathways, such as GABAergic transmission, or inhibit excitatory signals, leading to reduced muscle spasticity or spasms.
Advertisements
Classification of Centrally Acting Muscle Relaxants
-
GABAergic Drugs
- Drug: Diazepam
- Class: Benzodiazepine
- Mechanism: Facilitates GABA-A receptor activity → increases inhibitory neurotransmission
- Uses: Muscle spasms, anxiety, seizures
-
GABA-B Agonists
- Drug: Baclofen
- Mechanism: Activates GABA-B receptors in the spinal cord → reduces excitatory transmission to skeletal muscles
- Uses: Spasticity due to multiple sclerosis, spinal cord injury
-
α2-Adrenergic Agonists
- Drug: Tizanidine
- Mechanism: Centrally acting α2-adrenergic agonist → inhibits motor neurons in spinal cord
- Notes: Less sedating than clonidine
- Uses: Muscle spasticity, chronic pain
-
Others
- Cyclobenzaprine
- Structure: Related to tricyclic antidepressants (TCAs)
- Mechanism: Acts at brainstem level to reduce tonic somatic motor activity
- Use: Acute muscle spasm (e.g., trauma, strain)
- Methocarbamol, Carisoprodol, Chlorzoxazone
- Mechanism: Unclear; likely general CNS depressants
- Uses: Acute musculoskeletal conditions (e.g., low back pain, injuries)
- Cyclobenzaprine
Advertisements
Therapeutic Uses:
- Relief of painful musculoskeletal conditions, e.g., back pain, sprains
- Spasticity management in neurological disorders (e.g., cerebral palsy, multiple sclerosis, spinal cord injuries)
Adverse Effects:
- Sedation, dizziness, drowsiness (common due to CNS depression)
- Weakness, fatigue
- Dependency/abuse potential (notably with carisoprodol)
- Hypotension (notably with tizanidine)
Advertisements
