At present there is no drink what defecation cleansing fastest substance, you can drink polyethylene glycol, lactulose and other drugs for defecation cleansing. 1. Lactulose: it is an osmotic laxative used for the treatment of constipation and hepatic encephalopathy, which can stimulate gastrointestinal peristalsis, keep the bowels open, relieve the symptoms of constipation, and also reduce the absorption of ammonia, which is used for the treatment of hepatic encephalopathy or hepatic coma in the pre-comatose state. It is forbidden for patients with gastrointestinal obstruction, acute abdomen, gastrointestinal perforation and bleeding, hypokalemia, lactose intolerance. 2. Polyethylene Glycol: White granules or powder, an osmotic laxative used to treat constipation in adults and to prepare the bowel for cleansing before surgery and colonoscopy. There are adverse reactions such as diarrhea, nausea, bloating, rash, urticaria and edema. It is contraindicated in patients with hypersensitivity to the product, diseases of the small intestine or colon (gastric retention, intestinal perforation, gastrointestinal bleeding, toxic enteritis, congenital megacolon). There are many types of drugs for bowel cleansing, it is recommended to take them as prescribed by a doctor. All of the above drugs should be taken under the supervision of a doctor.