Abstract: Methotrexate is a folic acid antagonist commonly used in clinical practice for the treatment of autoimmune diseases. Its adverse effects include bone marrow suppression, abnormal liver function, and in severe cases, even life-threatening complications. We report a case of toxic reactions induced by methotrexate (MTX) taken for the treatment of hyperuricemia. The patient, a 54-year-old male, was admitted to the hospital with erythema, papules, and blisters on his limbs and trunk for six days, accompanied by erosion of the oral mucosa. Prior to admission, he had taken methotrexate 5 mg daily for hyperuricemia for one consecutive month, with a cumulative dose of 150 mg. He had also experienced bloody stools. Laboratory tests revealed decreased white blood cells, red blood cells, and platelets, elevated transaminase levels, and hypoalbuminemia. Diagnosis of methotrexate toxicity was made. Treatment included folic acid supplementation, promotion of excretion, urine alkalinization, stimulation of platelet and white blood cell production, anti-inflammatory therapy, hemostasis, liver protection, topical medications, and symptomatic supportive care. The patient improved and was discharged after nine days.

Key words: methotrexate toxicity, erythema multiforme