The compounds are substituted isocytosines which are histamine H.sub.2 -antagonists. Two specific compounds of the present invention are 2-\x9b2-(5-methyl-4-imidazolylmethylthio)-ethylamino!-5-(3-methoxybenzyl)-4-p\n' yrimidone and 2-\x9b2-(5-methyl-4-imidazolylmethylthio)ethylamino!-5-benzyloxy-4-pyrimidone\n' .
这些化合物是取代的异
胞嘧啶,是
组胺H.sub.2-拮抗剂。本发明的两种特定化合物是2-β2-(5-甲基-4-
咪唑基甲
硫基)-乙基
氨基-5-(3-甲氧基苄基)-4-
吡咯啉酮和2-β2-(5-甲基-4-
咪唑基甲
硫基)乙基
氨基-5-苄氧基-4-
吡咯啉酮。