From the Guidelines
Muscle relaxants work by relieving muscle spasms and pain.
Mechanism of Action
- They achieve this by inhibiting the transmission of nerve impulses that cause muscle contractions, thereby reducing muscle tone and relieving pain and discomfort.
- The exact mechanism of action may vary depending on the specific muscle relaxant, but most work by enhancing the effects of neurotransmitters such as gamma-aminobutyric acid (GABA) that inhibit nerve transmission 1.
Types of Muscle Relaxants
- Skeletal muscle relaxants, such as tizanidine, cyclobenzaprine, and carisoprodol, are commonly used to treat acute low back pain and are associated with central nervous system adverse effects, primarily sedation 1.
- Antispasticity drugs, such as baclofen and dantrolene, are used to treat muscle spasms caused by upper motor neuron syndromes, but have limited evidence for efficacy in low back pain 1.
Efficacy and Safety
- Skeletal muscle relaxants have been shown to be moderately superior to placebo for short-term pain relief in acute low back pain, but have insufficient evidence for long-term use or for chronic low back pain 1.
- Adverse events, such as sedation, drowsiness, and dizziness, are common with muscle relaxants, and serious complications, such as hepatotoxicity, can occur with certain medications 1.
From the Research
Mechanism of Action
- Muscle relaxants work by interfering with the normal signaling system between nerve and muscle, thereby paralyzing striated muscles that are under voluntary control 2
- They can be classified into two main categories: centrally acting skeletal muscle relaxants and peripherally acting muscle relaxants
- Centrally acting muscle relaxants, such as baclofen and tizanidine, work by stimulating receptors in the central nervous system, which in turn reduces muscle tone and relieves spasticity 3, 4
- Peripherally acting muscle relaxants, such as dantrolene, work by directly acting on the muscle itself, reducing muscle contraction and relieving spasms 3, 5
Types of Muscle Relaxants
- Skeletal muscle relaxants, such as cyclobenzaprine, carisoprodol, and orphenadrine, are used to treat musculoskeletal conditions, such as acute back or neck pain 3
- Antispasticity drugs, such as baclofen and dantrolene, are used to treat spasticity associated with upper motor neuron syndromes, such as multiple sclerosis 3, 4
- Benzodiazepines, such as diazepam and alprazolam, can also be used as muscle relaxants, although their use is often limited by their potential for abuse and dependency 4, 6
Efficacy and Safety
- There is fair evidence that certain muscle relaxants, such as baclofen, tizanidine, and cyclobenzaprine, are effective in relieving spasticity and musculoskeletal pain 3
- However, the use of muscle relaxants is often limited by their potential side effects, such as sedation, drowsiness, and dry mouth 3, 4
- Some muscle relaxants, such as dantrolene, have been associated with rare but serious side effects, such as hepatotoxicity 3, 5