Nausea and vomiting (emesis) are the most common adverse effects experienced by cancer patients undergoing chemotherapy treatment. Until the discovery of a group of anti-emetic drugs (5-HT3 antagonists), there was little to prevent this distressing side-effect and many patients refused chemotherapy because of it. During a course of chemotherapy, patients can suffer from emesis on the day of chemotherapy and for up to five days thereafter.

Some patients even suffer the day prior to chemotherapy in anticipation of what is to come. Other chemotherapy regimens are given over consecutive days (fractionated chemotherapy) in an attempt to lower the daily dose to reduce side effects and increase efficacy.