Single doses of up to 750 mg/m2 irinotecan have been given to patients with various cancers. The adverse events in these patients were similar to those reported with the recommended dosages and regimens. There have been reports of overdosage at doses up to approximately twice the recommended therapeutic dose, which may be fatal. The most significant adverse reactions reported were severe neutropenia and severe diarrhea. Maximum supportive care should be instituted to prevent dehydration due to diarrhea and to treat any infectious complications. There is no known antidote for overdosage of irinotecan.