Sensitivity reactions, including anaphylactic reaction, facial edema and urticaria, reported rarely. Use with caution in patients allergic to other 5-HT~3~ receptor antagonists (cross-reactivity reported). Acute, usually reversible ECG alterations and/or risk of altered cardiac conduction (use with caution in patients at risk of QT prolongation and/or ventricular arrhythmia). Prolongation of PR, QTc, and JT intervals and widening of the QRS complex observed. Should be used with caution in patients who have or may develop prolongation of cardiac conduction intervals, particularly QTc, including those with congenital QT syndrome, those with uncorrected hypokalemia or hypomagnesemia, patients receiving diuretics which may induce electrolyte abnormalities, patients receiving antiarrhythmic agents or other drugs which alter cardiac conduction (e.g. prolong QT interval), and those receiving cumulative high-dose anthracycline therapy. For chemotherapy-related emesis, it should be used on a scheduled basis. The drug is not intended for treatment of nausea and vomiting or for chronic continuous therapy. No dosage adjustment for dolasetron necessary in hepatic or renal impairment, although the apparent plasma clearance of hydrodolasetron is substantially reduced following oral and I.V. dolasetron in severe renal impairment and following I.V. administration of the drug in severe hepatic impairment.