Pharmacological characterization of positive inotropic derivatives of 4-amino-7-methyl-1,8-naphthyridine-3-carboxylic acid.

The positive inotropic effect of a series of 4-amino-7-methyl-1,8-naphthyridine-3-carboxylic acid derivatives was compared with the effects of known inotropic agents (ouabain, dihydroouabain, isoproterenol, adrenaline, histamine and isobutylmethylxanthine) in guinea-pig atrial and ventricular myocardial preparations. With respect to their functional effects, the 1,8-naphtyridine compounds are clearly different from drugs acting on the cAMP system, whereas several similarities with cardiac glycoside effects were found