Acting Muscle Relaxants

The discoveiy of centrally acting muscle relaxants dates back to 1910 when antodyne (3-phenoxy-1,2-propanediol) first gained its entry into the therapeutic armamentarium as an analgesic and antipyretic ad later on as skeletal muscle relaxant. In 1946, Berger and Bradley observed the muscle relaxant activity present in a large number of glycerol monoethers and analogues. 

As of now practically all the centrally acting muscle relaxants seem to depress neuronal activity instead of stimulating the inhibitory nerves. 

As stated earlier they are used to relieve painful muscle spasms and spasticity. They relax the muscle without impairing respiration centrally. They have sedative effects. Some have predominantly tranquilizing effect and are classified as such. 

In the following sections some typical examples belonging to different categories of the above class of compounds are described, namely  

A number of a-substituted glycerol ethers possessing potent centrally acting muscle relaxant properties have been used clinically. 

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StmcturaHy related to nitrofurantoias are Dantrolene [7261-97-4] (38), a peripherally acting muscle relaxant, and its analogues (39), which can be used as an antidote against succiaylcholine-iaduced myopathy and ia autoimmune myasthenia gravis therapy (136,137). 

J -methylpyrrolidone by conversion to the imine ( 7) by sequential reaction with triethyloxonium tetraf1uoroborate and then anhydrous ammonia. When this is reacted with 2,6-dimethyl-phenyl i socyanate, the centrally acting muscle relaxant xilobam (8) is formed. ... 

Therapeutic Function Centrally acting muscle relaxant... 

Suxamethonium sensitivity," prolonged paralysis of respiratory muscle function caused by failure to cleave the short-acting muscle relaxant succinylcholine widely used in anesthesia, was made testable with a simple bedside assay in 1968 (Motulsky and Morrow). However, that test was not incorporated widely into practice. Most anesthesiologists felt they could simply monitor all patients and "bag" those not resuming respiratory action, without testing for a trait that would be found in only one of 2000 patients. 

CENTRALLY ACTING MUSCLE RELAXANTS AND ANTIPARKINSONISM AGENTS 15... 

Since 1958, chlormezanone was marketed by Sanofi-Winthrop, under the brand name Trancopal, as a centrally acting muscle relaxant in lower back pain [22,23]. Evidence of the efficacy of chlormezanone was, however, limited and of poor quality. In comparison to other centrally acting muscle relaxants in lower back pain, there... 

Centrally acting muscle relaxants (A) lower muscle tone by augmenting the activity of intraspinal inhibitory interneurons. They are used in the treatment of painful muscle spasms, e.g., in Ltillmann, Color Atlas of Pharmacology 2000 Thieme All rights reserved. Usage subject to terms and conditions of license. 

Direct-acting muscle relaxants directly block the process of contraction of the muscle fibers themselves. Of all the direct-acting myotropic drugs, only dantrolene is used in medical practice. 

Centrally acting muscle relaxants are also widely used (baclofen, cyclobenzaprin, carisoprodol, methocarbamol, chlorphenesin, chlorzoxazone, orphenadrine, and... 

It is doubtful if combination drugs with centrally acting muscle relaxant substances can be given a general recommendation. Carisoprodol is me-... 

II. Centrally acting muscle relaxants Mephenesin Chlorzoxazone (MOBIZOX) 250 mg TDS... 

Diazinon exposure may interfere with the short-acting muscle relaxant, succinylcholine, used concurrently with anesthetics. The action of succinylcholine is terminated by means of its hydrolysis by serum cholinesterase (Klaassen et al. 1986). Since serum cholinesterase is strongly inhibited by diazinon (Davies and Holub 1980b Edson and Noakes 1960 Klemmer et al. 1978 Williams et al. 1959), it is possible that concurrent exposure to diazinon may result in the prolongation of the action of succinylcholine leading to prolonged muscular paralysis. 

Bielik, N., Kocsis, P., Farkas, S. Whole-cell patch-clamp analysis of the effect of RGH-5002, a novel centrally acting muscle relaxant drug on voltage-gated sodium channels of dorsal root ganglion neurons, Naunyn Schmiedeberg s Arch. 1997, 356, Suppl 1, R25. 

Farkas, S., Kocsis, P., Bielik, N. Comparative characterisation of the centrally acting muscle relaxant RGH-5002 and tolperisone and of lidocaine based on their effects on rat spinal cord in vitro, Neurobiology 1997, 5, 57-58. 

An extensive study of Fessenden69 is concerned with biological effects of twelve pairs of carbamates (64a/64b-75a/75b) (Table 9), each pair differing by only one atom (silicon in place of carbon). The most prominent of this series is the centrally acting muscle relaxant and tranquilizer meprobamate (66a). 

A 73-year-old woman had rhabdomyolysis, cholestatic hepatitis, and mild renal insufficiency 14 days after she started to take the centrally acting muscle relaxant chlorzoxazone while also taking simvastatin (79). Withdrawal of the causal medication and conservative therapy with volume substitution and forced diuresis was followed by almost complete resolution of the symptoms. 

Kobayashi H, Hasegawa Y, Ono H. Cyclobenzaprine, a centrally acting muscle relaxant, acts on descending serotonergic systems. EurJ Pharmacol. 1996 311 ... 

Suxamethonium is a depolarizing short-acting muscle relaxant that is rapidly hydrolysed by pseudocholinesterase, and drugs or chemicals that inhibit this enzyme may prolong its action. 

The centrally acting muscle relaxants have an onset of action ranging from 30 minutes to an hour. They reach their maximum concentration in the blood between 1-8... 

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