RESUMEN
OBJECTIVE: To evaluate the safety, tolerance, and pharmacokinetics of dolasetron mesylate and its active metabolite hydrodolasetron when dolasetron mesylate was administered intravenously at increasing infusion rates. DESIGN: A double-blind, placebo-controlled, parallel-group study. METHODS: Forty-nine healthy nonsmoking male volunteers were randomly assigned to receive intravenous doses of dolasetron mesylate 100 mg or placebo. Three groups of 16 subjects each (12 dolasetron mesylate, 4 placebo) received escalating infusion rates (50, 100, then 200 mg/min). Physical examinations, vital signs, laboratory tests, and adverse events were recorded before and after administration of the study drug. Serial blood samples and 12-lead electrocardiogram measurements were obtained for 24 hours after the infusion. Plasma samples were analyzed for dolasetron and hydrodolasetron. RESULTS: Dolasetron mesylate was well tolerated, with no apparent differences in vital signs or adverse event profiles among the different rates of infusion. In general, the pharmacokinetics of dolasetron and hydrodolasetron were superimposable among the three infusion rate groups. Plasma dolasetron concentrations declined rapidly in all three infusion rate groups, with mean elimination half-life (t1/2) of less than 10 minutes. The reduced metabolite hydrodolasetron, which accounts for most pharmacologic activity, formed rapidly, with maximum concentrations occurring between 0.4 and 0.5 hours and disappeared with a mean t1/2 of 8-9 hours. The correlation coefficients of least-squares regression analysis between the pharmacokinetic parameters and the infusion rate of dolasetron were less than 0.083 and the slopes were not significantly different from 0, suggesting that none of the hydrodolasetron pharmacokinetic parameters were affected by rate of infusion. CONCLUSIONS: The intravenous administration of dolasetron 100 mg over 0.5-2 minutes did not significantly alter the pharmacokinetic profiles of either dolasetron or hydrodolasetron. In addition, the safety profile of dolasetron did not change with increasing rate of infusion. Therefore, the rate of infusion of dolasetron mesylate appears to have no pharmacokinetic or clinical implications when assessed over a 0.5-2-minute time period.