Abstract: Phthalazone derivatives of the formula ##STR1## wherein R.sup.4 represents a carbamoyl group, a dialkylaminoalkylcarbamoyl group, a hydroxyalkylcarbamoyl group, an alkylidenehydrazinocarbonyl group, a hydrazinocarbonyl group, an alkylhydrazinocarbonyl group, a formyl group, a hydrazonomethyl group, an alkylhydrazonomethyl group, a hydroxyiminomethyl group, a dialkylhydrazonomethyl group or an alkylidenehydrazonomethyl group; R.sup.6, R.sup.7 and R.sup.8 each represent an alkyl group; and process for preparing same. The phthalazone derivatives are useful for the treatment and prevention of cerebral apoplexy, myocardial infarction and the like.

Abstract: A pharmaceutically active phthalzone derivative of the following formula ##SPC1##Wherein each of R.sub.1 and R.sub.2 is a member selected from the group consiting of alkyl of from 1 to 3 carbon atoms; R.sub.3 is a member selected from the group consiting of alkyl of from 1 to 5 carbon atoms with the proviso that R.sub.3 can form together with R.sub.2 a member selected from the group consiting of methylene, methyl-substituted and ethyl-substituted methylene. This compound is effectie for treating hypertension, thrombosis and athroscllerosis. A process for its preparation and a pharmaceutical composition containing it are also provided.