Antiemetic effects of Lerisetron in radiation-induced emesis in the dog

The 5-HT3 receptor antagonists are the most potent antiemetics known at pre sent. Lerisetron is a new 5-HT3 receptor antagonist chemically unrelated to other antagonists like Ondansetron. An emesis model in the dog induced by irradiation with Co-60 was used, and 8 Gy were administered over the total body surface. An irradiated control group was established and received no m edication, and two irradiated groups received treatment with either Ondanse tron or Lerisetron. The 'up-down' technique was employed to determine the e ffective dose (ED50). A logarithmic scale was used to increase or decrease the doses in each case. The initial doses were 300 mu g/kg for Ondansetron and 100 mu g/kg for Lerisetron. All animals in the control group vomited. T he ED50 of Ondansetron was 178 +/- 151 mu g/kg body wt and that of Lerisetr on was 63 +/- 18 mu g/kg. Lerisetron is more potent and presented less indi vidual variability than Ondansetron, but its antiemetic effects were equall y effective.