The effect of ondansetron on radiation-induced emesis and diarrhoea.

Fractionated radiotherapy of malignancies in the abdomen induces nausea and vomiting in approximately 50% of the patients. During abdominal irradiation the damaged gastrointestinal mucosa releases 5-HT with ensuing activation of 5-HT3 receptors which may explain the nausea and vomiting. Ondansetron is a new 5-HT3-antagonist with antiemetic properties. In this consecutive study, 33 patients receiving fractionated upper abdominal irradiation (> or = 100 cm2, 1,8-4 Gy daily dose for a mean of 13 days) were treated with ondansetron (8 mg t.d.s. p.o.). Emesis was completely controlled in 26/33 (79%) patients throughout their radiation course, which embraced 628 (94%) treatment days. Ondansetron was well tolerated. Eleven patients developed mild constipation. No patients experienced diarrhoea (a common distressing side-effect of abdominal irradiation). It is suggested that ondansetron can be of value in preventing emesis in patients receiving fractionated radiotherapy. The possible beneficial effect in preventing diarrhoea must be further evaluated.