Abstract: Novel substituted pyrazine derivatives are disclosed having the general formula (I): ##STR1## where R.sub.1 and R.sub.2 may be methyl, methoxy, halogen (particularly chlorine, bromine or fluorine), or hydrogen, with the proviso that R.sub.1 and R.sub.2 cannot both be hydrogen, and X may be S or NH.These novel substituted pyrazine derivatives show a remarkable activity as inhibitors of platelet aggregation at very low dosages.

Abstract: A process is disclosed for the preparation of a compound of the formula I ##STR1## where R is hydrogen or methyl, X is sulphur or the NH group, Y is selected from the class consisting of methyl, methoxy, chlorine, bromine, iodine, nitro or cyano, m is 0, 1 or 2, and n is 1 or 2, characterized in that a compound of the formula II: ##STR2## where R and n have the above-mentioned meanings, is reacted in a suitable polar aprotic solvent, such as dimethylforamide or dimethylsulphoxide, under a nitrogen atmosphere and at a temperature between 50.degree. and 100.degree. C, with the sodium salt of an appropriate 2-aminopyridine or 2-mercaptopyridine to give, after evaporation of the solvent in vacuo, the desired compound of formula I which is then purified by methods known "per se".The invention also includes the compounds of general formula I, where R, X, Y, m and n have the same meanings, and their pharmaceutically acceptable salts.