Skeletal Muscle Relaxants

Skeletal muscle relaxants are used to treat conditions involving hyperexcitable skeletal muscle.
These conditions include spasticity following CNS lesions and muscle spasms from musculoskeletal injuries.
The main goal is to normalize muscle hyperexcitability without significantly decreasing muscle function.
This normalization helps decrease pain and improve motor function.

Two primary categories:
- Agents to decrease spasms.
- Agents to decrease spasticity.
Muscle relaxants can act at different levels:
- Centrally (spinal cord and brain).
- Neuromuscular junction.
- Directly within the skeletal muscle fiber.

One of the oldest medications for muscle spasms related to musculoskeletal injuries.
Mechanism of action is centrally mediated:
- Inhibits alpha motor neuron activity at the spinal cord level.
- Induces general sedation in the brain.
Properties:
- Anxiolytic (anti-anxiety).
- Anticonvulsant.
- Relieves spasticity and muscle spasms (e.g., low back strains).
Can be a life-saving measure for laryngeal spasms associated with tetanus toxin.
Primary adverse effect: Sedation.
- Beneficial for short-term management of muscle spasms by promoting inactivity and healing.
Long-term use is discouraged due to:
- Sedation and associated fall risk.
- Risk of physical dependence.

Examples include cyclobenzaprine (Flexeril) and carisoprodol (Soma).
Mechanism of action is not well-understood, but may involve increasing global CNS sedation, leading to skeletal muscle relaxation.
Typically used as adjuncts to rest and physical therapy for short-term relief of muscle spasms from acute musculoskeletal injuries.
Often given with analgesics like acetaminophen or aspirin.
Long-term use should be discouraged due to sedative properties and potential for abuse.