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 cisplatin-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 dexamethasone 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, respectively. 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 were 90.4%/92.3% and 61.3% 72.7%. There was no significant difference in antiemetic efficacy between both arms. Decreased incidence of and delayed onset of nausea on day 2 were observed in arm B (p = 0.002). The emetic severity during previous CT correlated significantly with those of the subsequent CT. The complete control of nausea/vomiting was maintained in 81.6%/72.1% of arm C patients during the following 3rd-6th cycles of CT. CONCLUSION No difference in antiemetic efficacy was shown when a triple 8 mg dose of ondansetron was given at 4-hourly intervals or at 24-hourly intervals. However, the latter improved nausea on day 2. A single 8 mg dose of ondansetron can maintain antiemetic efficacy in the majority of complete responders in arm A and arm B.