Compounds of the general formula (I) ##STR1## and physiologically acceptable salts, hydrates and bioprecursors thereof have been found to show pharmacological activity as selective histamine H.sub.2 -antagonists. The substituents in Formula (I) are defined in the specification.
通式(I)##STR1##及其生理上可接受的盐、
水合物和
生物前体已被发现具有作为选择性
组胺H.sub.2-拮抗剂的药理活性。在公式(I)中的取代基在说明书中有定义。