Lactulose is a synthetic disaccharide which is metabolized in the colon by bacterial flora, producing short chain fatty acids including lactic acid and acetic acid. These products of lactulose metabolism acidify the colonic contents, thus favouring the formation of ammonium ions from ammonia. The ions can not be absorbed, and are trapped in the colon until they are excreted in the faeces. This effectively reduces plasma ammonia concentrations.
a synthetic disaccharide that causes acidification of the colonic environment when it is fermented by bacteria. This environment promotes the conversion of ammonia to ammonium and the latter ions are not easily absorbed due to their electrical charge. The trapped ammonia is therefore excreted in faeces. Lactulose is also a cathartic laxative that reduces the amount of time available for colonic bacteria to act on surplus amino acids.