Clinical studies with ondansetron in the control of radiation-induced emesis.

Ondansetron is a 5-HT3 receptor antagonist which has shown activity in the prevention of nausea and vomiting resulting from cytotoxic therapy. This paper describes the results of studies evaluating the efficacy of oral ondansetron in controlling radiation-induced emesis. Initial non-randomised studies showed that doses of 4 mg q.d.s. or 8 mg t.d.s. of ondansetron achieved complete or major control of vomiting in 77-91% of patients and mild or absence of nausea in 72-77% following single exposure high-dose (8-10 Gy) radiotherapy to the upper abdomen. A subsequent double-blind, prospective, randomised trial compared ondansetron 8 mg t.d.s. with metoclopramide 10 mg t.d.s. in the prevention of emesis following single radiation doses of 8-10 Gy to the upper abdomen. On the day of radiotherapy, ondansetron achieved significantly greater control of vomiting and retching (P less than 0.001) and nausea (P = 0.001) than metoclopramide. An advantage for ondansetron was also seen on days 2 and 3 after irradiation, although this did not reach a statistically significant level. Only two patients, out of 154, in all the studies experienced side effects attributable to ondansetron: one developed headache and the other experienced headache and vertigo. These studies show that ondansetron is a safe drug, with activity in the prevention of radiation-induced emesis and significantly greater efficacy than metoclopramide in the control of nausea and vomiting following single exposure upper abdominal high-dose radiotherapy.