THE PATTERN OF EMESIS FOLLOWING HIGH-DOSE CYCLOPHOSPHAMIDE AND THE ANTIEMETIC EFFICACY OF ONDANSETRON

Two randomized, double-blind placebo-controlled ondansetron dose ranging studies in patients receiving high-dose cyclophosphamide (with or without doxorubicin) were completed in the US. These studies enable the pattern of emesis and nausea for 3 days following high-dose cyclophosphamide to be described and give some insight into the mechanisms of emesis which may be operating. Nausea and vomiting induced by cyclophosphamide-based chemotherapy has a long latency of onset (8-13 h) and continues for at least 3 days. These findings are of particular importance as many of these patients receive chemotherapy as outpatients and emphasize the need for appropriate anti-emetic prophylaxis for patients at home. Ondansetron was extremely effective over this time in the control of emesis and nausea. These results suggest that high-dose cyclophosphamide-induced emesis over days 1-3 is largely mediated via 5-hydroxytryptamine (5-HT) and 5-HT3 receptors.