Kyorin Pharmaceutical Co., Ltd.

Taroh Tooru

Katsuya Awano

Kayoko Matsuzawa

Yasushi Kouno

Takenobu Ogata

Novel pyrazolopyridylpyridazinone derivatives characterized by being represented by general formula (1) and pharnacologically acceptable salts thereof, which exhibit a phosphodiesterase inhibiting activity and have a selective potent bronchodilating effect on the respiratory tract; a process for the preparation of them; and bronchodilators containing the same as the active ingredient; wherein R,is C,-C,lower alkyl or C,-C,cycloalkyl; and R,, R,, R,and R,are each independently hydrogen, C,-C,lower alkyl or phenyl, or alternatively R,and R,may be united to form a double bond.

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Nogi-machi, Japan

Taroh Tooru