Takeda Chemical Industries, Inc.

Shojiro Yurugi

Shintaro Kikuchi

Novel pyrido (3,4-d) pyridazines shown by the general formula: ##STR1## wherein R is a lower alkoxy group or a halogen atom and their pharmaceutically acceptable salts are excellent in diuretic properties, and are useful to human therapy of edema and hypertension.

Pyrido (3,4-d)pyridazines

Novel 8-alkylpyrido[3,4-d]pyridazines of the formula: ##STR1## wherein R.sup.1 stands for a lower alkyl group; R.sup.2 stands for a cyclic amino group, or pharmaceutically acceptable salts thereof, have excellent diuretic activity in mammals including human beings, so that they are useful for therapy for human or animal use.

8-Alkylpyrido[3,4-d]pyridazines

Novel 7-(hydroxyphenyl)pyrido(3,4-d)pyridazines of the formula: ##STR1## wherein R.sup.1 stands for hydrogen or a lower alkyl group; R.sup.2 stands for a cyclic amino group, or a pharmaceutically acceptable salt thereof, have excellent diuretic activity in mammals including human beings, so that they are useful for therapy for human or animal use.

7-(Hydroxyphenyl)pyrido(3,4-d)pyridazines

A pyrido [3,4-d] pyridazine derivative is provided herein of the formula: ##SPC1## Wherein R.sub.1 is hydrogen or an alkyl group of 1 to 4 carbon atoms; R.sub.2 is an alkyl group of 1 to 4 carbon atoms, an aralkyl group of 7 to 8 carbon atoms, or a substituted or unsubstituted phenyl, naphthyl, furyl or pyridyl, the substituent being a lower alkoxy group of 1 to 3 carbon atoms, a lower alkyl group of 1 to 3 carbon atoms, halogen or nitro; R.sub.3 is hydrogen or a lower alkoxy group of 1 to 4 carbon atoms; and R.sub.4 is a substituted or unsubstituted morpholino, piperidino or pyrrolidino, the substituent being methyl or ethyl and a pharmaceutically acceptable salt thereof. The compounds of the present invention have effective and strong diuretic action and exhibit extremely low toxicity characteristics.

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Kyoto, Japan

Shojiro Yurugi