TPMT and Decreased total leukocyte count: Several factors, including the influence of the therapeutic dose of AZA and the co-administration of 5-ASA, which is commonly used to induce and maintain remission, suggest that 5-ASA inhibits TPMT and interacts with AZA, potentially leading to increased 6-TGN levels in 82% to 100% of patients, suggesting greater therapeutic efficacy, but also a higher risk of leukopenia [5,16,32,34,41].