167Original Article Intravenous Ondansetron plus Intravenous Dexamethasone with Different Ondansetron Dosing Schedules during Multiple Cycles of Cisplatin-based Chemotherapy

Background: This study examined whether different ondansetron dosing schedules plus dexamethasone influenced antiemetic efficacy during multiple cycles of cis-platin-based chemotherapy (CT). Antiemetic activities between previous CT and subsequent cycles were compared. Methods: The cross-over study involved 424 patients. Arm A, three doses of 8 mg ondansetron given intravenously (IV) at 4-hourly intervals plus dexametha-sone 20 mg IV at the start of CT, followed by dexamethasone 5 mg IV every 12 hours. Arm B, as arm A but the three doses of 8 mg ondansetron were given at 24-hourly intervals. For those with complete protection from emesis in both arms, a single dose of 8 mg ondansetron (arm C) was tried during the following CT. Once complete protection of emesis could not be maintained, arm A regimens were administered in the subsequent cycles of CT. Results: There were 384, 377 and 147 patients in arm A, arm B and arm C, respec-tively. Complete control of acute and delayed nausea/vomiting obtained in arm A were 91.4%/94.8 % and 59.6%/70.1%, and in arm B wer