The optimal dose of ondansetron as premedication for moderately or highly emetogenic chemotherapy

Abstract

8209 Background: Anti-emetic guidelines recommend the use of a serotonin-receptor antagonist for the prevention of acute emesis prior to the administration of highly or moderately emetogenic chemotherapy. However, dosages of these agents, such as ondansetron, vary throughout the literature. Our trial was undertaken to determine the optimal dosage of ondansetron in terms of anti-emetic efficacy and safety while keeping in mind a cost-conserving perspective. Methods: In this single institution study, all patients scheduled to receive moderately or highly emetogenic chemotherapy (Hesketh criteria ≥ 3) in a six month period for various cancer types were eligible. Ondansetron 32mg I.V. was administered prior to the first cycle of chemotherapy. De-escalation of the dosage to 24mg and 16mg I.V. occurred with cycles two and three, respectively. Acceptable response was defined as no emesis or mild nausea. Failure was defined as ≥1 episodes of emesis or nausea lasting more than 30 minutes. Efficacy and side effects were monitored for 24 hrs. McNemar test for repeated measures was used to compare dosage responses. Results: A total of 52 patients were properly enrolled. 35 patients received a Hesketh 5 regimen, 16 patients received a Hesketh 4 regimen, and 1 patient received a Hesketh 3 regimen. Acceptable response rates were 86.5% in the 32mg group, 78.8% in the 24mg group, and 63.5% in the 16mg group. When we compared the 32mg vs. the 24mg group in terms of acceptable versus failed response there was no statistical difference (p= 0.22). However, statistical differences were significant when comparing the 24mg vs. the 16mg group (p=0.02) and the 32mg vs. the 16mg group (p=0.001). All three doses of ondansetron were well tolerated with no unexpected drug-related adverse effects. Headache was the most commonly reported side effect and occurred in 23% of the patients. Conclusions: Despite our small sample size, differences in efficacy became apparent once the dosage was de-escalated below 24mg. Although lower dosages are more cost efficient, 24mg should be the minimal dosage of ondansetron administered prior to moderately or highly emetogenic chemotherapy. No significant financial relationships to disclose.