ADJUSTING THE DOSE OF INTRAVENOUS ONDANSETRON PLUS DEXAMETHASONE TO THE EMETOGENIC POTENTIAL OF THE CHEMOTHERAPY REGIMEN

Purpose: This pilot, open-label study evaluates the antiemetic efficac y and safety of a single 20-mg intravenous (IV) dose of dexamethasone combined with a single IV dose of ondansetron (32, 24, or 8 mg) in pat ients receiving highly emetogenic (HE), moderately high emetogenic (MH E), or moderately emetogenic (ME) chemotherapy, respectively. Patients and Methods: One hundred forty-six patients received a single 20-mg I V dose of dexamethasone over 15 minutes beginning 45 minutes before ch emotherapy and either a single 32-, 24-, or 8-mg IV dose of ondansetro n over 15 minutes beginning 30 minutes before chemotherapy. Patients w ere evaluated for emetic episodes, extent of nausea, and adverse event s for 24 hours after chemotherapy. Results: Complete response (no emet ic episodes) was noted in 72% (95% confidence interval [Cl], 60% to 84 %), 88% (95% Cl, 79% to 97%), and 77% (95% Cl, 63% to 92%) of patients in the HE, MHE, and ME categories, respectively. The proportion of pa tients who experienced no nausea on the posttreatment assessment was 5 1% (95% Cl, 37% to 64%), 69% (95% Cl, 56% to 81%), and 47% (95% Cl, 29 % to 65%), respectively. The antiemetic regimens were all well tolerat ed. The proportion of patients with any drug-related adverse events di d not vary across the three study groups despite the range of ondanset ron doses and variety of chemotherapy regimens. Mild headache was note d in 28% of patients. Other adverse events, all of which were noted in fewer than 10% of patients, included lightheadedness, fatigue, dizzin ess, and constipation. Conclusion: A single IV dose of either 8, 24, o r 32 mg of ondansetron combined with a single 20-mg IV dose of dexamet hasone resulted in good control of acute emesis across a wide spectrum of chemotherapy regimens. Nausea control proved somewhat more difficu lt, with approximately 50% of patients in the HE and ME emetogenic cat egories experiencing some degree of nausea. The results of our pilot s tudy suggest that adjusting the dose of ondansetron to the intrinsic e metogenicity of the chemotherapy regimen permits a more efficient use of ondansetron while maintaining good antiemetic control. Such an appr oach appears worthy of further investigation. (C) 1995 by American Soc iety of Clinical Oncology.