warnings and cautions
5 WARNINGS AND PRECAUTIONS Hypersensitivity Reactions, Including Anaphylaxis and Bronchospasm : Discontinue ondansetron if suspected. Monitor and treat promptly per standard of care until signs and symptoms resolve. ( 5.1 ) QT Interval Prolongation and Torsade de Pointes : Avoid ondansetron in patients with congenital long QT syndrome; monitor with electrocardiograms (ECGs) if concomitant electrolyte abnormalities, cardiac failure or arrhythmias, or use of other QT prolonging drugs. (5.2) Serotonin Syndrome : Reported with 5-HT 3 receptor antagonists alone but particularly with concomitant use of serotonergic drugs. If such symptoms occur, discontinue ondansetron and initiate supportive treatment. If concomitant use of ondansetron with other serotonergic drugs is clinically warranted, patients should be made aware of a potential increased risk for serotonin syndrome. ( 5.3 ) Myocardial Ischemia : Monitor or advise patients for signs and symptoms of myocardial ischemia after oral administration. ( 5.4 ) Masking of Progressive Ileus and/or Gastric Distension Following Abdominal Surgery or Chemotherapy-Induced Nausea and Vomiting : Monitor for decreased bowel activity, particularly in patients with risk factors for gastrointestinal obstruction. ( 5.5 ) Phenylketonuria: Patients should be informed that ondansetron orally disintegrating tablets contain phenylalanine (a component of aspartame). Each 4 mg orally disintegrating tablet contains 1.68 mg phenylalanine and 8 mg orally disintegrating tablet contains 3.37 mg phenylalanine. ( 5.6 ) 5.1 Hypersensitivity Reactions Hypersensitivity reactions, including anaphylaxis and bronchospasm, have been reported in patients who have exhibited hypersensitivity to other selective 5-HT 3 receptor antagonists. If hypersensitivity reactions occur, discontinue use of ondansetron; treat promptly per standard of care and monitor until signs and symptoms resolve [see Contraindications (4) ] . 5.2 QT Prolongation Electrocardiogram (ECG) changes, including QT interval prolongation have been seen in patients receiving ondansetron. In addition, postmarketing cases of Torsade de Pointes have been reported in patients using ondansetron. Avoid ondansetron in patients with congenital long QT syndrome. ECG monitoring is recommended in patients with electrolyte abnormalities (e.g., hypokalemia or hypomagnesemia), congestive heart failur...