Pyridazinone and pyrazolone compounds, cardiotonic compositions including same, and their uses

A compound of the formula ##STR13## wherein A is --C.dbd. or --N.dbd.;

• B is --C.dbd.C--, --C.dbd.N-- or --N.dbd.C--;
• provided that A or B represents a nitrogen-containing group;
• X is --(CR.sub.4 R.sub.5).sub.a --(O).sub.b --(CR.sub.6 R.sub.7).sub.c --;
• a and c are 0, 1 or 2;
• b and z are 0 or 1;
• provided that a+b+c=1,
• R.sub.n is hydrogen, alkyl, aralkyl, aryl, acyl, carbalkoxy, carbamyl, carbalkoxyalkyl, hydroxyalkyl, alkoxyalkyl, or amidino;
• R, R.sub.1, R.sub.2, R.sub.3, R.sub.5 and R.sub.6 are hydrogen, alkyl, or aralkyl;
• R.sub.4 is hydrogen, alkyl, aryl, or aralkyl;
• R.sub.7 is hydrogen, alkyl, aralkyl, aryl, acyl, carbalkoxy, carbalkoxyalkyl, hydroxyalkyl, alkoxyalkyl, amidino, alkoxy, amino, nitro, carboxy, cyano, alkyl amino, halo, hydroxy, mercaptyl, alkyl mercaptyl, carboalkyl or carbamoyl;
• R and groups on vicinal carbon atoms may together form a carbon-carbon double bond provided that R.sub.n is hydrogen and z=1;
• R.sub.6 and R.sub.7 geminal groups may together form a spiro substituent, --(CH.sub.2).sub.d --, where d is 2 to 5;
• R.sub.2 is hydrogen or --(CH.sub.2).sub.y --Y where y is 1-3;
• Y is hydrogen, --O--R.sub..alpha., --S--R.sub..alpha. or --NR.sub..alpha. R.sub..beta. ;
• R.sub..alpha. is hydrogen, alkyl or acyl;
• R.sub..beta. is hydrogen or alkyl;
• R.sub..alpha. and R.sub..beta. together with the nitrogen atom to which they are attached may form a 3-7 membered ring which may also contain 0-2 additional N, O or S atoms;
• or a pharmaceutically acceptable salt thereof.