New congeners of antihypertensive and antithrombotic 7-amino or 7-acetyl-aminosubstituted-4,4a-dihydro-5H-indeno (1,2-c)pyridazin-3-ones.

New congeners of the antihypertensive and antithrombotic 7-amino-(I b) and 7-acetylamino-4,4a-dihydro-5H-indeno(1,2-c)pyridazin-3-one (I c) have been synthesized and evaluated pharmacologically. Compounds (I k) (R = 7-NHCH3), (I l) (R = 7-N(CH3)COCH3) and (I m) (R = 7-N(CH3)COC2H5) exhibited an antihypertensive effect similar to that of (I b) and (I c), though short lasting. The antithrombotic activity of six compounds was found comparable to or higher than that of acetylsalicilic acid. In particular, (I l) and (I m) fully protected mice against thrombosis, as did the reference compound (I c).