Compounds useful for the treatment of patients suffering from muscle spasms of the formula (I) ##STR1## in which R represents the radical ##STR2## in which R.sub.1, in any position on the phenyl nucleus, represents a linear, branched or cyclic alkyl, alkenyl or alkynyl, containing up to 8 carbon atoms, or the radical ##STR3## in which R.sub.2 and R.sub.3, identical or different each represents a hydrogen atom, a linear alkyl, alkenyl or alkynyl, containing up to 8 carbon atoms, or form together with the nitogen atom to which they are joined, a heterocyclic radical optionally containing another heteroatom, or NO.sub.2, or OR', R' representing hydrogen, a linear, branched or cyclic alkyl containing up to 8 carbon atoms, or aryl containing up to 14 carbon atoms, or an SR.sub.4 or S(O)R.sub.5 radical, R.sub.4 and R.sub.5 representing a linear, branched or cyclic alkyl, alkenyl or alkynyl, containing up to 8 carbon atoms, or R represents naphthyl, optionally substituted by an R.sub.1 radical, as defined above; also therapeutic compositions containing the same and method of use.