Overdose of methotrexate can lead to serious adverse effects such as haematopoietic disorders (leukopenia, thrombocytopenia, anaemia, and pancytopenia) and gastrointestinal reactions (mucositis, stomatitis, oral ulceration, gastrointestinal ulceration, and gastrointestinal bleeding). Some reports of overdose have been fatal. In these fatal cases, events such as sepsis or septic shock, renal failure, and aplastic anaemia were reported.
