Dystonias muscle relaxants

Botox (Toxin) Muscle relaxation activity, cervical dystonia Botulinum sp. 

Most muscle relaxants are absorbed fairly easily from the gastrointestinal tract, and the oral route is the most frequent method of drug administration. In cases of severe spasms, certain drugs such as methocarbamol and orphenadrine can be injected intramuscularly or intravenously to permit a more rapid effect. Likewise, diazepam and dantrolene can be injected to treat spasticity if the situation warrants a faster onset. As discussed earlier, continuous intrathecal baclofen administration may be used in certain patients with severe spasticity, and local injection of botulinum toxin is a possible strategy for treating focal dystonias and spasticity. Metabolism of muscle relaxants is usually accomplished by hepatic microsomal enzymes and the metabolite or intact drug is excreted through the kidneys. 

Botulinum toxin has been used for some time to control localized muscle dystonias, including conditions such as spasmodic torticollis, blepharospasm, laryngeal dystonia, strabismus, and several other types of focal dystonias.6 25,26,87 93 When used therapeutically, small amounts of this toxin are injected directly into the dystonic muscles, which begin to relax within a few days to 1 week. This technique appears to be fairly safe and effective in many patients, but relief may only be temporary. Symptoms often return within 3 months after each injection, necessitating additional treatments.40 Still, this technique represents a method for treating patients with severe, incapacitating conditions marked by focal dystonias and spasms. 

In recent years the ability of bofulinum toxin to cause muscle paralysis has been harnessed in the treatment of numerous disease conditions in which the abnormality is sustained muscle contraction or spasm. These conditions are collectively termed dystonias. Its usefulness depends on the fact that it can be injected into individual muscles to block neuromuscular transmission, which results in relaxation of the affected muscles. It was first used therapeutically by Scott in 1973, who was able to correct strabismus, or squint, in a patient by injecting it into the muscles of the eye (Figure 2). Since then it has been used to treat a large number of... 

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