Abstract: To provide an intimal hyperplasia inhibitor useful for prevention of restenosis after percutaneous transluminal coronary angioplasty (PTCA) or vascular stent placement or treatment of its progress. An intimal hyperplasia inhibitor containing a 3(2H)-pyridazinone compound represented by the formula (I): [wherein each of R1, R2 and R3 is independently a hydrogen atom or a C1-6 alkyl group, X is a halogen atom, cyano or a hydrogen atom, Y is a halogen atom, trifluoromethyl or a hydrogen atom, and A is a C1-8 alkylene which may be substituted with a hydroxyl group] or a pharmacologically acceptable salt thereof.

Abstract: To provide an antineutrophilia agent effective for treatment of development and progress of acute infections, collagen diseases (chronic rheumatoid arthritis, Wegener's granulomatosis and Behcet's disease), chronic obstructive pulmonary disease (COPD), chronic bronchitis, pulmonary emphysema, small airway disease, gout, Cushing's syndrome, myelofibrosis, neoplastic neutrophilia, polycythemia vera and diseases caused by administration of steroid drugs. An antineutrophilia agent containing a 3(2H)-pyridazinone compound represented by the formula (I) or a pharmaceutically acceptable salt thereof [wherein each of R1, R2 and R3 is independently a hydrogen atom or a C1-6 is alkyl group, X is a halogen atom, cyano or a hydrogen atom, Y is a halogen atom, trifluoromethyl or a hydrogen atom, and A is a C1-8 alkylene which may be substituted with a hydroxyl group].

Abstract: An intimal hyperplasia inhibitor containing a 3(2H)-pyridazinone compound represented by the formula (I): [wherein each of R1, R2 and R3 is independently a hydrogen atom or a C1-6 alkyl group, X is a halogen atom, cyano or a hydrogen atom, Y is a halogen atom, trifluoromethyl or a hydrogen atom, and A is a C1-8 alkylene which may be substituted with a hydroxyl group] or a pharmacologically acceptable salt thereof.

Abstract: To provide an antineutrophilia agent effective for treatment of development and progress of acute infections, collagen diseases (chronic rheumatoid arthritis, Wegener's granulomatosis and Behcet's disease), chronic obstructive pulmonary disease (COPD), chronic bronchitis, pulmonary emphysema, small airway disease, gout, Cushing's syndrome, myelofibrosis, neoplastic neutrophilia, polycythemia vera and diseases caused by administration of steroid drugs. An antineutrophilia agent containing a 3(2H)-pyridazinone compound represented by the formula (I) or a pharmaceutically acceptable salt thereof [wherein each of R1, R2 and R3 is independently a hydrogen atom or a C1-6 alkyl group, X is a halogen atom, cyano or a hydrogen atom, Y is a halogen atom, trifluoromethyl or a hydrogen atom, and A is a C1-8 alkylene which may be substituted with a hydroxyl group].

Abstract: Pyridazinone derivatives represented by the formula (I) and antiplatelet agents containing them: ##STR1## ?wherein R is a hydrogen atom or a C.sub.1 -C.sub.4 alkyl group, X is a hydrogen atom, a chlorine atom or a bromine atom, Ar is a pyridyl group or a phenyl group substituted with OR.sup.1 (wherein R.sup.1 is a hydrogen atom or a C.sub.1 -C.sub.4 alkyl group) and A {wherein A is a hydrogen atom, a halogen atom, a C.sub.1 -C.sub.4 alkyl group or OR.sup.2 (wherein R.sup.2 is a hydrogen atom or a C.sub.1 -C.sub.4 alkyl group)}, Y is C.sub.1 -C.sub.8 alkylene wherein one carbon atom on the straight chain is substituted with one OR.sup.1 group (wherein R.sup.1 is the same as defined above), and Z.sup.1 and Z.sup.2 are independently a hydrogen atom, a halogen atom, a C.sub.1 -C.sub.4 alkyl group or a OR.sup.1 group (wherein R.sup.1 is the same as defined above)!.

Abstract: An agent for the prophylaxis or treatment of TXA.sub.2 -mediated diseases, particularly, a TXA.sub.2 synthetase inhibitor, which comprises a pyridazinone compound of the formula (I) ##STR1## wherein each symbol is as defined in the specification, or a pharmacologically acceptable salt thereof as an active ingredient. The pyridazinone compound (I) and pharmacologically acceptable salts thereof used in the present invention have prophylactic and therapeutic activities against TXA.sub.2 -mediated diseases, particularly a TXA.sub.2 synthetase inhibitory action and are useful as an agent for the prophylaxis or treatment of TXA.sub.2 -mediated diseases, particularly as TXA.sub.2 synthetase inhibitors.

Abstract: Pyridazinone derivatives represented by the formula (I) and antiplatelet agents containing them: ##STR1## ?wherein R is a hydrogen atom or a C.sub.1 -C.sub.4 alkyl group, X is a hydrogen atom, a chlorine atom or a bromine atom, Ar is a pyridyl group or a phenyl group substituted with OR.sup.1 (wherein R.sup.1 is a hydrogen atom or a C.sub.1 -C.sub.4 alkyl group) and A {wherein A is a hydrogen atom, a halogen atom, a C.sub.1 -C.sub.4 alkyl group or OR.sup.2 (wherein R.sup.2 is a hydrogen atom or a C.sub.1 -C.sub.4 alkyl group)}, is C.sub.1 -C.sub.8 alkylene wherein one carbon atom on the straight chain is substituted with one OR.sup.1 group (wherein R.sup.1 is the same as defined above), and Z.sup.1 and Z.sup.2 are independently a hydrogen atom, a halogen atom, a C.sub.1 -C.sub.4 alkyl group or a OR.sup.1 group (wherein R.sup.1 is the same as defined above)!.

Abstract: A compound of the formula, ##STR1## or its pharmaceutically acceptable salt, and its preparation process and pharmaceutical compositions characterized by containing these compounds as effective ingredients.These compounds have strong antithrombotic activity, cardiotonic activity, vasodilator activity and anti-SRS-A activity, and are useful as prophylactic or therapeutic agents for various thrombotic affections, congestive heart failure, hypertension, asthma, immediate type allergy diseases and the like.

Abstract: A compound of the formula: ##STR1## or its pharmaceutically acceptable salt and pharmaceutical compositions containing these compounds as effective ingredients. These compounds have strong antithrombotic activity, cardiotonic activity, vasodilator activity and anti-SRS-A activity, and are useful as prophylactic or therapeutic agents for various thrombotic afflictions, congestive heart failure, hypertension, asthma, immediate-type allergy diseases and the like.

Abstract: A compound of the formula, ##STR1## or its pharmaceutically acceptable salt, and its preparation process and pharmaceutical compositions characterized by containing these compounds as effective ingredients.These compounds have strong antithrombotic activity, cardiotonic activity, vasodilator activity and anti-SRS-A activity, and are useful as prophylactic or therapeutic agents for various thrombotic affections, congestive heart failure, hypertension, asthma, immediate type allergy diseases and the like.

Abstract: A pyrazolo[4,3-d]pyrimidine derivative having the formula: ##STR1## wherein R.sup.1 is lower alkyl or phenyl which is unsubstituted or substituted by lower alkyl, lower alkoxy or halogen; R.sup.2 is a saturated or unsaturated, straight chain or branched aliphatic group having from 2 to 22 carbon atoms or phenyl-lower alkyl with the phenyl group unsubstituted or substituted by lower alkyl, lower alkoxy or halogen; and A is an alkylene group having from 1 to 3 carbon atoms which is unsubstituted or substituted by methyl, or a pharmaceutically acceptable salt thereof.

Abstract: A pyrazolo[4,3-d]pyrimidine derivative having the formula: ##STR1## wherein R.sup.1 is lower alkyl or phenyl, R.sup.2 is --A--CO.sub.2 R.sup.21 (wherein A is alkylene having from 1 to 10 carbon atoms which is unsubstituted or substituted by alkyl having from 1 to 3 carbon atoms; and R.sup.21 is lower alkyl having from 1 to 4 carbon atoms), --CH.sub.2 CO-phenyl, a saturated or unsaturated, straight chain or branched aliphatic group having from 3 to 16 carbon atoms, phenyl-lower alkyl, --CH.sub.2 CN, chloro substituted phenyl-lower alkyl or ##STR2## (wherein R.sup.22 is hydrogen or lower alkyl), and R.sup.3 is a saturated or unsaturated, straight chain or branched aliphatic group having from 2 to 22 carbon atoms, phenyl-lower alkyl, benzyloxy substituted phenyl-lower alkyl, lower alkyl substituted or unsubstituted 2-(phenylmethyloxy)ethyl, cyclohexylcyclohexyl, methylcyclohexyl, 3-thia-n-heptyl, 3,6-dioxa-n-decyl, 4-oxo-n-pentyl or 2-hydroxyethyl.

Abstract: A compound of the formula: ##STR1## wherein R is methyl or ethyl, X is hydrogen (provided R is ethyl), lower alkyl, lower alkoxy, lower alkylthio, fluorine, bromine, phenoxy or substituted phenoxy, X.sub.m is methylenedioxy or --CH.dbd.CH--CH.dbd.CH--, and m is 1, 2 or 3.