Derivatives of isosorbid mononitrate, utilization as vasodilator agents with reduced tolerance

Novel derivatives of isosorbide mononitrate and its pharmaceutically acceptable salts, which have vasodi-lating activity with a reduced effect of tolerance, of the general formula (I) in which A and B independently represent any of the groups-ON02 and -Z-CO-R, wherein Z is an oxygen atom or sulphur atom and R is an alkyl C1-C4 group, an aryl group or an aralkyl group eventually substituted, or the group in which R1 is hydrogen, or an alkyl C1-C4 group, an aryl group or an aralkyl group, eventually substituted, with the proviso that one of A or B is always -ON02, but never both of them at the same time, when Z is an sulphur atom R is an alkyl C1-C4 group, an aryl group or an aralkyl group, eventually substituted, and when Z is an oxygen atom R is the group