Magnesium sulfate 50 grams immediately after drinking water, so as to fully cleanse the intestinal tract and prevent dehydration. Because magnesium sulfate is not easily absorbed by the intestinal tract, it can stay in the intestinal lumen to promote intestinal peristalsis, so magnesium sulfate has a laxative effect and can be used to induce diarrhea, which needs to be dissolved in water when used. Generally before the colonoscopy, the subject may need to drink magnesium sulfate to cleanse the intestines as prescribed by the doctor. And magnesium sulfate 50 grams immediately after drinking water, if it is not enough water or too long interval, may not play the role of intestinal cleansing, and because diarrhea may lead to the loss of body water, so if magnesium sulfate 50 grams after drinking water immediately, and may cause dehydration. In addition, if there is acute intestinal obstruction and other conditions of patients, it is not appropriate to use magnesium sulfate to cleanse the intestines, diarrhea, so as not to aggravate the symptoms of intestinal obstruction and so on. It is recommended to consult a doctor before using the drug, and then under the guidance of the doctor reasonable use of magnesium sulfate, etc., so as not to be detrimental to health.