2,4-Diaminoquinazolines as antithrombotic agents

A method of inhibiting platelet aggregation in a warm-blooded animal in need of such inhibition which comprises parenterally administering to said animal an effective and non-tonic amount of a compound of the formula, ##STR59## wherein R.sub.1 and R.sub.2 are monovalent groups independently selected from the group consisting of

• a. ##STR60## wherein R.sub.4 and R.sub.5 independently are selected from the group consisting of hydrogen, C.sub.1 -C.sub.3 alkyl, and cycloalkyl having fewer than about 12 carbon atoms, with the proviso that when either R.sub.4 or R.sub.5 is hydrogen the remaining group cannot be C.sub.1 -C.sub.3 alkyl, and that both R.sub.4 and R.sub.5 cannot be cycloalkyl;
• b. ##STR61## wherein R.sub.6, R.sub.7, and R.sub.8 independently are selected from the group consisting of hydrogen and C.sub.1 -C.sub.3 alkyl and A is a polymethylene group;
• and
• c. monocyclic heterocyclic-amino consisting of substituted or unsubstituted five- or six-membered single hterocyclic rings having no more than about 12 atoms and containing one nitrogen hetero atom and one oxygen hetero atom as the only hetero atoms;
• with the proviso that at least one of R.sub.1 and R.sub.2 must be selected from group (c);
• and R.sub.3 is selected from the group consisting of hydrogen, chlorine, and methyl, and physiologically-acceptable salts thereof.

A method of inhibiting platelet aggregation in a warm-blooded animal in need of such inhibition which comprises parenterally administering to said animal an effective and nontoxic amount of a compound of the formula, ##STR62## wherein R.sub.1 and R.sub.2 are monovalent groups independently selected from the group consisting of

• a. ##STR63## wherein R.sub.4 and R.sub.5 both are either hydrogen or identical C.sub.1 -C.sub.3 alkyl groups, or one of R.sub.4 and R.sub.5 is hydrogen and the remaining group is cycloalkyl having fewer than about 12 carbon atoms;
• b. ##STR64## wherein R.sub.7 and R.sub.8 both are identical C.sub.1 -C.sub.3 alkyl groups and A is a polymethylene group;
• and
• c. monocyclic heterocyclic-amino consisting of unsubstituted five- or six-membered single heterocyclic rings containing one nitrogen hetero atom and one oxygen hetero atom as the only hetero atoms;
• with the proviso that at least one of R.sub.1 and R.sub.2 must be selected from group (c);
• and R.sub.3 is selected from the group consisting of hydrogen, chlorine, and methyl and is in the 6-position;
• and physiologically-acceptable salts thereof.