PYRIDAZINONE DERIVATIVE OR SALTS THEREOF

NEW MATERIAL:The compound of formula I [R is H or lower alkyl; R is lower alkyl, lower alkylthioalkyl, lower alkoxy, NH2 or mono- lower alkylamino which may have substituent group (selected from OH, lower alkoxy, NH2, mono- or di-lower alkylamino or 5-6-membered saturated cyclic amine containing 1-2 hetero atoms); R is H, lower alkyl, lower alkoxy, lower alkylthio, NH2, mono- or di-lower alkylamino, lower acylamino, CN, CF3, lower alkoxycarbonyl or CONH2; dotted line shows that the bond between the 4- and 5-positions of the pyridazinone ring is single or double bond] or its salt. EXAMPLE:The compound of formula IV. USE:A cardiotonic agent. PREPARATION:The compound of formula I which is one of the compounds of formula I can be produced by the substitution reaction of the compound of formula II and the compound of formula III (X is halogen; R is lower alkyl or lower alkoxy).