2-Amino-5-Chlorobenzoxazole (McN-485, Flexin), A Long-Acting Spinal Cord Depressant.

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Abstract
McN-485 was shown previously to produce prolonged flaccidity resembling that obtained for short periods with mephenesin (3-0-toloxy-l,2-propanediol) in unanesthetized animals. In the present study its effects on spinal reflexes and indirectly stimulated muscle were studied in spinal cats. Quantitive comparison of depressant action on the flexor reflex was made between McN-485 and 5 pharmacologically similar compounds (1) mephenesin, (2) 2,2-diethyl-1,3-propanediol (Prenderol), (3) 2-amino-6-methylbenzothiazole, (4) benzimidazole and (5) 2-methyl-2-n-propyl-l,3-propanediol dicarbamate (Miltown). McN-485 produced selective depression of polysynaptic reflexes at lower doses than those required to block monosynaptic reflexes; in much higher doses, it inhibited the response of indirectly stimulated skeletal muscle. In these respects it resembled the other 5 drugs tested. However, its duration of action was extremely protracted, and its potency was considerably greater than those of the other 2 long-activity compounds (4,5). The drug appears to possess desirable properties as a potential agent for treating conditions associated with skeletal muscle spasm.