There is no specific antidote for ondansetron overdose. Patients should be managed with appropriate supportive therapy. Individual doses as large as 150 mg and total daily dosages (three doses) as large as 252 mg have been administrated intravenously without significant adverse events. These doses are more than 10 times the recommended daily dose. In addition to the adverse events listed above, the following events have been described in the setting of ondansetron.
Overdose: *Sudden blindness* (amaurosis) of 2 to 3 minutes duration plus severe constipation occurred in one patient that was administered 72 mg of ondansetron intravenously as a single dose. Hypotension (and faintness) occurred in another patient that took 48 mg of oral ondansetron. Following infusion of 32 mg over only 4-minute period, a vasovagal episode with transient second-degree heart block was observed. In all instance, the events resolved completely.