FUSED PYRIDAZINE COMPOUNDS

A fused pyridazine compound represented by the following general formula (I) or a pharmacologically acceptable salt thereof: (see formula I) wherein R1 is halo, optionally substituted lower alkyl, optionally substituted lower alkoxy, optionally substituted cycloalkyl, nitro, cyano, optionally substituted amino, optionally substituted alcohol, optionally substituted thiol or optionally protected carboxyl; n is 0 to 4; A is hydrogen, halo, optionally substituted amino, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted arylalkyl or optionally substituted heteroarylalkyl; X is nitro or optionally substituted amino; Y is carbonyl or substituted carbene; and C is a five- or six-membered ring which may contain a heteroatom; which exhibits an inhibitory activity against cyclic GMP phosphodiesterase (hereinafter referred to as "cGMP-PDE"). The compounds are useful as preventive and therapeutic agents for diseases for which a cGMP-PDE inhibiting action is efficacious, for example, ischemic heart diseases such as angina pectoris, myocardial infarct and chronic and acute cardiac failure, pulmonary hypertension, arteriosclerosis and bronchial asthma.