Compounds or their salts of general formula (I): A-B-N(O).sub.s wherein: s is an integer equal to 1 or 2; A=R-T.sub.1-, wherein R is the drug radical and T.sub.1=(CO).sub.t or (X).sub.t', wherein X=O, S, NR.sub.1c, R.sub.1c is H or a linear or branched alkyl or a free valence, t and t' are integers and equal to zero or 1, with the proviso that t=1 when t'=0; t=0 when t'=1; B=-T.sub.B-X.sub.2--O-- wherein T.sub.B=(CO) when t=0, T.sub.B=X when t'=0, X being as above defined; X.sub.2 is equal to R.sub.1B-X-R.sub.2B radical wherein X is as above defined, R.sub.1B and R.sub.2B, equal to or different from each other, are linear or branched C.sub.1-C.sub.6 alkylenes, or X.sub.2 is a radical wherein two alkylene chains C.sub.1-C.sub.4 are linked to nonadjacent positions of a central ring having 4 or 6 atoms, said ring being an unsaturated cycloaliphatic ring, or a saturated or aromatic heterocylic ring, containing one or two heteroatoms, equal or different, selected from O, S, N; wherein the unsaturated cycloaliphatic ring does not have aromatic character according to Huckel's rule.