Absorption: Owing to hepatic first-pass metabolism, its bioavailability is only about 60%.
Distribution: Plasma protein binding of ondansetron as measured in vitro was 70% to 76%, over the pharmacologic concentration range of 10 to 500 ng/mL. Circulating drug also distributes into erythrocytes.
Metabolism: Ondansetron is extensively metabolized in humans, with approximately 5% of a radiolabeled dose recovered as the parent compound from the urine. The primary metabolic pathway is hydroxylation on the indole ring followed by subsequent glucuronide or sulfate conjugation.
Elimination: In adult cancer patients, the mean ondansetron elimination half-life was 4.0 hours, and there was no difference in the multidose pharmacokinetics over a 4-day period.
Prevention of nausea and vomiting associated with highly emetogenic chemotherapy, including cisplatin ≥50mg/m2.
Prevention of nausea and vomiting associated with initial and repeat courses of moderately emetogenic chemotherapy.
Prevention of nausea and vomiting associated with radiotherapy in patients receiving total body irradiation, single high-dose fraction to the abdomen, or daily fractions to the abdomen.