Nissan Chemical Industries Limited

Hitoshi Nakabeppu

Keizo Tanikawa

Hiroo Matsumoto

Nobutomo Tsuruzoe

Takashi Matsumoto

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)!. These compounds have strong antiplatelet effects, are excellently safe, and can be used as active ingredients of prophylactic and therapeutic drugs for various thrombotic diseases.

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Shiraoka-machi, Japan

Hitoshi Nakabeppu