**This is a synthetic disaccharide which is metabolised by the acidifying colonic bacteria. Ammonia is converted into ammonium ions, which cannot be absorbed and hence trapped in the colon and excreted in the faeces. [[Drugs Acting on the Intestines#Osmotic Laxatives|Lactulose]] also acts as an osmotic laxative, allowing more faeces and bacteria to be washed out. | **This is a synthetic disaccharide which is metabolised by the acidifying colonic bacteria. Ammonia is converted into ammonium ions, which cannot be absorbed and hence trapped in the colon and excreted in the faeces. [[Drugs Acting on the Intestines#Osmotic Laxatives|Lactulose]] also acts as an osmotic laxative, allowing more faeces and bacteria to be washed out. |