Lactulose is a synthetic disaccharide drug, mainly used in the treatment of constipation and hepatic encephalopathy. Lactulose can promote intestinal peristalsis, increase intestinal osmotic pressure, adsorb intestinal bacteria, and soften feces, which is helpful to promote constipation and relieve constipation and other symptoms of constipation patients with difficulty in defecation. Under the action of intestinal bacteria, lactulose is decomposed into acetic acid and lactic acid with low pH value, which can reduce the absorption of blood ammonia, and the increase of blood ammonia can cause hepatic encephalopathy, therefore, lactulose is helpful for the treatment of cirrhosis and hepatic encephalopathy patients. Adverse reactions such as diarrhea, bloating and nausea may occur during the administration of Lactulose, and it should be noted that Lactulose should not be used in cases of allergy, intestinal obstruction, acute abdomen, uremia, pregnancy and so on. It should be used under the guidance of a physician, and is prohibited for private use.