3,6-Disubstituted-5,7-(lower alkano)-5,6,7,8-tetrahydropyrido(4,3-C)pyridazines; their intermediates, preparation, antihypertensive use and compositions

Substituted pyridazines of formula I (I), wherein A denotes a lower alkylene group, R1 denotes an optionally-substituted or derivatized amino group, R2 denotes an alkyl group, an alkoxy group, an alkylmercapto group, an optionally-substituted aryl group, a phenalkoxy group or an optionally-substituted amino group and X denotes an oxygen atom or a sulfur atom, and their acid-addition salts with inorganic and organic acids are new compounds. They have an anti-hypertensive effect and are suitable for the treatment of hypertension. Processes for the preparation of the new, pharmacologically-effective compounds, new intermediate products required for their preparation, therapeutic use of the compounds, compositions for such use and unit dosage forms of the compositions are disclosed.