Before the colonoscopy is done usually drink compound polyethylene glycol electrolyte dispersion, because this drug is a hypertonic drug, while the taste is relatively poor, so it can easily lead to symptoms of nausea and vomiting. If nausea and vomiting still occur, metoclopramide hydrochloride injection 10mg can be given intramuscularly. If there is no relief from medication, ondansetron or granisetron injection can be given intravenously, and chlorpromazine injection should be given intramuscularly. To prevent electrolyte disorders, intravenous potassium chloride, sodium chloride and calcium gluconate should be given to prevent water-electrolyte disorders. Most of these medications are usually given for complete relief.