Evaluation of therapeutic drug monitoring of methotrexate in saliva of children with rheumatic diseases

Pediatric patients with leukemia, other malignancies, and rheumatological disease receive methotrexate chronically. Because of the documented correlation between methotrexate levels of compliance and clinical outcome, it is conceivable to verify appropriate systemic exposure to the drug. Saliva sampling may be of potential interest, especially in children, in whom blood sampling is ethically limited. Our study shows poor correlation between serum total/free methotrexate concentrations and saliva levels, precluding the clinical use of this test.