Adverse effects are also as expected with sedation and dizziness. The mechanism of action of both metaxalone and methocarbamol are unknown but are likely due to their general CNS depressant effects.Despite this, metaxalone seems to have less sedation than other muscle relaxants, and little abuse potential.The muscle relaxant class is a heterogeneous group of agents, with individual differences in drug interactions, comorbidity considerations, and ADEs.These agents are categorized as either antispasmodics or antispasticity agents.It has been shown to cause anemia so it is contraindicated in patients with any type of anemia, as well as any patient with liver or kidney compromise.It is metabolized via several hepatocellular cytochrome P450 (CYP450) enzyme families; however, it has not been shown to be an inducer or an inhibitor.At this time, guidelines do not recommend chronic use of muscle relaxants for musculoskeletal pain.Antispasmodic Agents Agents that fall into this category act at the spinal cord or supraspinal level.
The antispasticity agents reduce hypertonicity associated with upper motor neuron disorders like multiple sclerosis and cerebral palsy.
Methocarbamol elimination is significantly reduced in patients with hepatic or renal impairment, and has been shown to interfere with the effects of pyridostigmine bromide and should not be used in patients with myasthenia gravis.
Orphenadrine is similar in structure to diphenhydramine and its effects are thought to be due to its anticholinergic properties.
The skeletal muscle relaxants are a diverse class of drugs that are used for treating painful muscle spasticity or spasms, which can substantially affect a patient’s ability to function (Table 1).
About 2 million people annually report using muscle relaxants, with about 15% being elderly.