Muscle Spasm
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 Muscle Spasm?

Muscle spasm is defined as a sudden involuntary contraction of one or more muscle groups and is usually an acute condition associated with muscle strain (partial tear of a muscle) or sprain (partial or complete rupture of a ligament). Common musculoskeletal conditions causing tenderness and muscle spasms include fibromyalgia, tension headaches, myofascial pain syndrome, and mechanical low back pain or neck pain. If muscle spasm is present in these conditions, it is related to local factors involving the affected muscle groups.

The skeletal muscle relaxants flexeril, carisoprodol, chlorzoxazone, cyclobenzaprine, metaxalone, methocarbamol, and orphenadrine are approved for treatment of musculoskeletal disorders.

Clinical studies show, that cyclobenzaprine, carisoprodol, orphenadrine, and tizanidine are effective compared to placebo in patients with musculoskeletal conditions (primarily acute back or neck pain). Cyclobenzaprine has been evaluated in the most clinical trials and has consistently been found to be effective.

Muscle relaxant

A muscle relaxant is a drug which affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasms, pain, and hyperreflexia. The term "muscle relaxant" is used to refer to two major therapeutic groups: neuromuscular blockers and spasmolytics. Neuromuscular blockers act by interfering with transmission at the neuromuscular end plate and have no CNS activity. They are often used during surgical procedures and in intensive care and emergency medicine to cause paralysis. Spasmolytics, also known as "centrally-acting" muscle relaxants, are used to alleviate musculoskeletal pain and spasms and to reduce spasticity in a variety of neurological conditions. While both neuromuscular blockers and spasmolytics are often grouped together as muscle relaxants,[1][2] the term is commonly used to refer to spasmolytics only.

The two primary categories of skeletal muscle relaxants are anti-spastic agents (eg, baclofen [Kemstro and Lioresal] or dantrolene [Dantrium]) for diseases like cerebral palsy, spastic torticollis, and multiple sclerosis and anti-spasmodic agents for muscle-related conditions. 

Anti-spastic agents are rarely used for musculoskeletal conditions; however, some rheumatologists report success in treating fibromyalgia using baclofen. Since this is an "off-label" use, caution should be exerted and the lowest possible doses should be prescribed... and then only by specialists who have much experience. Patients should be informed as to the potential side effects.