Posts Tagged ‘Brain Stem’

Muscle Relaxants and Its Usage

September 30th, 2010
kelly price asked:




A drug which decreases muscle tone by affecting skeletal muscle function is known as muscle relaxant. It blocks the transmission of nerve impulses or decreases excitability of motor-end plate or uses other ways to reduce muscle contractility. To put in a layman’s language, it is a drug which relieves and relaxes muscle tension.

Most of us may not be aware that muscle relaxants were used as early as 16th century in the South American continent. Arrow tips were dipped in poison to produce skeletal muscle paralysis which eventually leads to death. The present muscle relaxants are based on these principles. Those poison tipped arrows used curare as their poison. Curare was used in earlier studies of pharmacology as well. It has tubocurarine which was used in research of neuromuscular transmission.

Muscle relaxants are broadly classified in two categories as follows:-

Spasmolytics: Spasmolytics are also called as centrally acting muscle relaxants. It gets its name for it reduces spasticity in many neurological conditions. Spasmolytics normally act at brain stem, cortex and spinal cord or even all the three areas and hence they are called as muscle relaxants which act centrally. Spasmolytics are also known as antispasmodic and are commonly used for low back pain, neck pain and headaches related to tension.

Neuromuscular Blockers: Neuromuscular blockers interfere with transmission at the neuromuscular end plate. These types of muscle relaxants have no CNS activity. They are normally used in intensive care units and surgical procedures. They are also used as an emergency medicine for causing paralysis. At around 1940, doctors started using neuromuscular-blocking medicines as muscle relaxants during surgeries.

Factors taken into consideration while choosing a muscle relaxant are side effects, efficiency, tolerance and cost. Adverse effects are a major worry for all muscle relaxants. These effects include drowsiness, dizziness and some major effects on our bodies as well. These drugs are recommended upon their tolerability with cost being a minor concern as efficiency is what people seem to look for.

Dantrolene is used for neurological conditions like multiple sclerosis and cerebral palsy. Rapid muscle contraction is more sensitive as compared to a muscle which contracts gradually. Dantrolene can have major effects like normal muscle weakness, sedation, and hepatitis in some cases. Carisoprodol, metaxalone, cyclobenzaprine and methocarbamol are commonly used for myofascial pain syndrome, fibromyalgia, low back and neck pain.



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Muscle Relaxants For Low Back Pain

June 3rd, 2010
Yury Bayarski asked:




Muscle relaxants are one of the many treatments used in the management of low back pain. About thirty-five percent of patients visiting a physician for low back pain are prescribed skeletal muscle relaxers.

For acute low back pain, muscle relaxaers improve pain, muscle tension, and mobility more effectively than a placebo does. For chronic low back pain, they may relieve pain and lead to overall improvement. However, side effects are common.

The term “muscle relaxants” is very broad and includes a wide range of drugs with different indications and mechanisms of action. Muscle relaxants can be divided into two main categories: antispasmodic and antispasticity medications.

Antispasmodics are used to decrease muscle spasm associated with painful conditions such as back pain. Antispasmodics can be subclassified into benzodiazepines and nonbenzodiazepines. Benzodiazepines (e.g., alprazolam, diazepam, tetrazepam) are used as anxiolytics, sedatives, hypnotics, anticonvulsants, and skeletal muscle relaxants.

Non-benzodiazepines include a variety of drugs that can act at the brain stem or spinal cord level. The mechanisms of action with the central nervous system are still not completely understood.

Carisoprodol and metaxalone have moderate antispasmodic effects and are mildly sedative. Carisoprodol blocks interneuronal activity in the descending reticular formation and spinal cord. Carisoprodol is metabolized to meprobamate. Meprobamate was introduced as an antianxiety agent in 1955 and is prescribed primarily to treat anxiety, tension, and associated muscle spasms. Its onset and duration of action are similar to the intermediate-acting barbiturates. Excessive use can result in psychological and physical dependence.

Cyclobenzaprine is structurally similar to the tricyclic antidepressants; however, it has strong side effects such as sedation. It is currently believed that cyclobenzaprine acts in the brain stem rather than at the spinal cord level. Cyclobenzaprine has anticholinergic activity (which is responsible for some side effects such as dry mouth).

The use of muscle relaxants for low back pain continues to be a source of controversy among physicians, mainly because of their side effects. In addition to sedation, potential side effects include drowsiness, headache, blurred vision, nausea, and vomiting. Potential for abuse and dependency has also great drawback. Some guidelines recommend these medications alone or in combination with NSAIDs as optional, others clearly do not recommend using these drugs. Despite this controversy, 91% of doctors report using muscle relaxants even if they are conditionally discouraged by guidelines.

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