Elderly people need to take oral cotrimoxazole for bowel clearance preparation before colonoscopy, and the specific use is divided into two types of administration on the day of the examination and the day before the examination. Copolyethylene glycol is mainly used for colorectal endoscopy and removal of intestinal contents before colorectal surgery. Therefore, the elderly need to take oral polyethylene glycol before colonoscopy. 1. On the day of the examination: fasting for breakfast on that day (water is allowed), and giving the medicine about 4 hours before the scheduled examination time. 2. Administration on the day before the examination: fasting after dinner on the day before (drinking water is allowed) and administration 1 hour after dinner. For breakfast and lunch on the first two days, you should eat food with little residue, and for dinner, you should eat a liquid diet that does not contain solid food. It is contraindicated in case of intestinal obstruction, intestinal perforation, gastric retention, gastrointestinal bleeding, toxic enteritis, toxic megacolon, and in case of allergy to the components of the product. Always follow the doctor’s advice before taking, do not take it on your own to avoid adverse consequences.