5-Ethyl-5-phenylbarbituric acid (I) [50-06-6], 3-(piperidinomethyl)-5-ethyl-5-phenylbarbituric acid [6733-91-1], 1,3-bis(piperidinomethyl)-5-ethyl-5-phenylbarbituric acid (II) [23192-91-8], 1,3-bis(piperidinomethyl)-5,5-diethylbarbituric acid [23192-92-9], 1,3-bis(morpholinomethyl)-5,5-diethylbarbituric acid [2052-91-7], but not 3-morpholino-5-ethyl-5-phenylbarbituric acid [18009-29-5] decreased phagocytosis in the reticuloendothelial system in mice.Only I and II suppressed hemagglutination when given i.p. prior to and after the antigen stimulus.