lactulose UK /ˈlak.tjʊ.ləʊz/US /ˈlæk.t(j)ʊˌloʊs/ noun1 •A synthetic disaccharide C₁₂H₂₂O₁₁ consisting of galactose and fructose units, used as a laxative for chronic constipation and as an acidifier to reduce blood ammonia levels causing neurological symptoms in advanced liver disease. It is used in solution for oral or rectal administration. formslactuloses