Toxicity and side effects of ondansetron

The safety of ondansetron has been carefully evaluated through laboratory studies and clinical trials. Preclinical studies demonstrated that there is no end-organ toxicity in rats and dogs administered ondansetron doses 30 to 100 times those used in humans. At near-lethal doses of ondansetron, animals developed subdued activity, ataxia, and convulsions. Modest transient increases in serum transaminase values were observed. Concurrent administration of ondansetron with chemotherapy had no effect on tumor response in animals. The clinical safety of ondansetron has been evaluated in more than 2,500 cancer patients who received intravenous doses as large as 1.5 mg/kg. In adult patients receiving single-day chemotherapy, the incidence of adverse events was 36% with ondansetron (n = 647) and 50% with metoclopramide (n = 498). Diarrhea occurred in 9% of ondansetron patients and 19% of metoclopramide patients. Headache occurred in 14% of ondansetron patients and 8% of metoclopramide patients. Extra-pyramidal symptoms were reported in none of the ondansetron patients and 5% of the metoclopramide patients. The incidence of vascular occlusive events and seizure disorders was nearly identical with ondansetron and metoclopramide and similar to the cancer population in general. In a group of 209 pediatric patients receiving chemotherapy, the incidence of adverse events was 19% with ondansetron. Serum transaminase values increased significantly in 6% to 8% of ondansetron patients and 2% of metoclopramide patients. There was no apparent relationship between the cumulative dose of ondansetron administered and the incidence of increased transaminase values. However, there was an apparent relationship between the cumulative dose of cisplatin administered and the incidence of transaminase abnormalities. These data demonstrate that ondansetron is better tolerated than metoclopramide and is safe for intravenous administration to pediatric and adult patients receiving chemotherapy.