Substituted isocytosines having histamine H.sub.2 -antagonist activity
 The compounds are substituted isocytosines which are histamine H.sub.2 -antagonists. Two specific compounds of the present inventon are 2-[2-(5-methyl-4-imidazolylmethylthio)ethylamino]-5-(3-pyridylmethyl)-4-py rimidone and 2-[2-(3-bromo-2-pyridylmethylthio)ethylamino]-5-(4-pyridylmethyl)-4-pyrimi done. 
Smith Kline & French Laboratories Limited
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inventional inventional inventional
Thomas H. Charon R. Graham J.
Brown Ganellin Durant