Just like the name suggests, muscle relaxants work to relax muscles. This is done by decreasing muscle tone in an attempt to counter symptoms such as spaticity and spasms. Muscle spasms occur when uncontrolled involuntary contractions are experienced at any muscle in the body causing pain. This is mainly associated with diseases such as tension headaches, fibromyalgia and myofascial pain syndrome. Spasticity on the other hand is when muscles contract tightly, become stiff and harden. Common diseases associated with spasticity include spinal cord injury, traumatic brain injury, poststroke syndrome and multiple sclerosis. Typically, muscle relaxants are used to treat acute or short-lived muscle problems but they may be used in treating chronic pain involving muscle spasms.
There are two major therapeutic groups that fall under muscle relaxants namely spasmolytics and neuromuscular blockers. The spasmolytics work directly on the central nervous system to reduce the stiffness of muscles and relieve spasm and pain. These are mainly used to deal with muscle problems associated with problems with the nerves. The neuromuscular blockers on the other hand act by stopping the transmission of information across the neuromuscular endplate resulting in temporary paralysis which is useful in performing surgical procedures.
There are many muscle relaxants in the market that though they may differ in chemical composition, the overall effects are the same. They include baclofen, diazepam, dantrolene, tizanidine, orphenadrine, metaxalone, cyclobenzaoprine, carsoprodol and methocarbamol among others. Diazepam and other benzodiazepines act by interacting with GABAA receptors and affect the levels of GABA which is a chemical messenger necessary for the passing of signals and information in the nervous system. Baclofen on the other hand is an agonist at the GABAB receptors of the brain and spinal cord. Tizanidine acts as an agonist to alpha-adrenergic receptors while the other drugs apply many other different mechanisms.
Muscle relaxants are available in different forms including capsules, syrup and tablets. Other formulations include Baclofen injection that is given intrathecally in the back, diazepam liquid massaged into the back for absorption via the rectum, cannabidiol which is available as a spray for the mouth. Regardless of the mode by which they are introduced into the body, muscle relaxants reach the blood stream from which they move to the musculoskeletal system where their effects are exhibited.
Muscle relaxants are very powerful drugs and tend to be associated with several side effects. The main is sedation and reduced alertness and people are advised not to operate machinery or drive after taking the drugs. Adverse effects especially when taken in high doses include heart failure and paralysis. Other side effects that commonly occur differ from drug to drug but all recommended drugs confer more benefits than harm to those who use them.