Constipation is one of the side effects associated with the use of Ondansetron. Some tips for dealing with constipation include drinking 8-10 glasses of non-alcoholic fluids a day, keeping the body active, and having fiber in your diet (fruits and vegetables). A stool softener once or twice a day may also prevent constipation. Please contact your clinician if you do not have a bowel movement for 2-3 days.