Methotrexate is a medication used to treat cancer, autoimmune diseases, and ectopic pregnancy. However, it can also cause toxicity in some patients. Methotrexate toxicity can occur due to various reasons, including overdose, impaired kidney or liver function, or interactions with other medications. Common symptoms of methotrexate toxicity include nausea, vomiting, diarrhea, mouth sores, fever, chills, fatigue, hair loss, skin rash, and dizziness. Severe toxicity can lead to bone marrow suppression, liver damage, kidney failure, lung inflammation, and even death [2]. Methotrexate toxicity can be prevented by closely monitoring the patient's blood counts, liver and kidney function, and avoiding interactions with other medications. In case of toxicity, the patient should stop taking methotrexate and seek medical attention immediately [3].

Sources:
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5585837/
[3] https://www.goodrx.com/methotrexate/mtx-methotrexate-toxicity