2-(3,5-Substituted-2-pyridylalkylamino)-5-oxopyridylmethyl-4-pyrimidones useful as histamine H.sub.1 -antagonists

A compound of formula (2) ##STR16## or a pharmaceutically acceptable salt thereof;

• where R.sup.1 is halogen, nitro, amino, C.sub.1-4 alkylamino, C.sub.1-4 alkanoylamino or C.sub.1-4 alkyl;
• R.sup.2 is halogen, nitro, amino, C.sub.1-4 alkylamino, C.sub.1-4 alkanoylamino, C.sub.1-4 alkyl or C.sub.3-4 alkoxy;
• provided that R.sup.1 and R.sup.2 are not both selected from amino, C.sub.1-4 alkylamino, C.sub.1-4 alkanoylamino and nitro;
• R.sup.3 is a C.sub.1-3 alkylene group;
• and
• R.sup.4 is a pyridone group in which the nitrogen atom is optionally substituted with a group R.sup.5, where R.sup.5 is C.sub.1-4 alkyl, hydroxy C.sub.1-4 alkyl, C.sub.1-4 alkoxy C.sub.1-4 alkyl, or phenyl-C.sub.1-4 alkyl optionally substituted by one hydroxy, halogen, C.sub.1-4 alkoxy or C.sub.1-4 alkyl;
• or is a 2- or 4- C.sub.1-4 alkoxy pyridyl group.