Voluntary Muscles
Your body depends on the work of involuntary muscles (such as your heart) and voluntary muscles (such as the major skeletal muscles in your arms and legs) to perform the mechanical actions of your body. When using a muscle relaxant, the medication specifically targets your voluntary muscles, causing them to decrease in tone and relax.
Types
Muscle relaxants can be broken down into two types: anti-spasmolytics and neuromuscular blockers. Spasmolytic drugs include prescriptions such as methocarbamol and benzodiazepines (such as lorazepam and diazepam). Neuromuscular blockers are typically only used in hospital settings and include medications such as mivacurium, succinylcholine and tubocurarine.
GABA
Many anti-spasmolytic muscle relaxants work as GABA (gamma-aminobutyric acid) agonists. This means they increase the activity of GABA receptors, which creates an inhibitory action forcing nerve impulses to slow down throughout the central nervous system. This causes the skeletal muscles to receive fewer signals and relax.
Signal Blocking
Neuromuscular blockers are more powerful medications that actually cause muscle paralysis. This is used during surgeries to ensure that unexpected muscle movement, whether voluntary or involuntary, doesn't cause serious complications during the procedure. Neuromuscular blockers work by blocking key neurotransmitters needed for muscles to move.
Side Effects
Muscle relaxants, especially those that act on the GABA receptors, often cause drowsiness. Take care when using muscle relaxant medications, and they should never be mixed with other central nervous system depressants, including alcohol. According to the American Academy of Family Physicians, certain muscle relaxants, such as benzodiazepines, also have high risk for dependence and abuse.
