The present invention relates to antithrombotic compounds 2-alkyl aryl sulphonyl-1,2,3,4-tetrahydro-9H-pyrido(3,4-b)indole-3-carboxylic acid esters/amides, pharmaceutically acceptable salts and compositions thereof to be used in the treatment of intravascular thrombosis such as myocardial ischemia and stroke. The compound has the following general structure ##STR00001## wherein R represents methyl ester or amide and R.sub.1 represents alkyl, aryl and heteroaryl moiety.