Introduction: Methotrexate, a structural analogue to the folic acid, is one of the most frequently used antimetabolites in pediatric oncologic pathology. Its mode of action and toxic effects are now well known. Material
and method: Our study aimed to describe the quantitation of the drug in serum of 40 children with acute lymphatic leukemia receiving high doses of methotrexate and to predict serum methotrexate levels at 96 hours, based on 48 h, 72h levels and on alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, and creatinine serum levels. The above mentioned parameters were analyzed by sampling serum levels at 48h, 72h and 96 hours after methotrexate administration and a logical regression model being projected upon obtained results. Results and conclusions: methotrexate serum level at 96 hours does not depend on either AST, ALT, urea, creatinine levels or on the methotrexate level determined at 48 hours, it only depends on the methotrexate serum level at 72 hours.