OBJECTIVE: To investigate the influencing factors of delayed excretion after high-dose methotrexate in chemotherapy of hematological malignant tumor and its correlation with adverse drug reactions. METHODS: Clinical data and blood concentration data were collected from 34 patients with hematological malignant tumor who received 71 high-dose methotrexate chemotherapy courses in the First People’s Hospital of Changzhou from Jul. 2016 to Jun. 2018.The influencing factors on MTX excretion at different time points were analysed

and the correlations between delayed excretion and adverse drug reactions in various systems were also investigated. RESULTS: At 48 h and 72 h after administration

the average blood concentration of methotrexate were respectively（ 1. 27 ± 2. 49） μmol/L and（ 0. 34±0. 48） μmol/L

with the excretion-delay rates were respectively 25. 71% and 30. 00%. The blood concentration of methotrexate in patients with delayed excretion at 48 h and 72 h after administration was significantly higher than that of patients with normal excretion

with statistically significant difference（ P<0. 01）; the dosage and body surface area dosage of methotrexate in patients with delayed excretion were significantly larger than those of patients with normal excretion

with statistically significant differences（ P < 0. 05）; compared with patients ≤ 60 years old

the elderly（ >60 years old） were more prone to delay in excretion at 72 h after administration（ P = 0. 003）. Liver injury was more likely to occur in patients with delayed excretion at 48 h after administration（ P = 0. 027）

but no significant effect of delayed excretion on the risk of other systemic adverse drug reactions was observed. CONCLUSIONS: Drug dosage and patient’s age have significant effects on delayed excretion of methotrexate

and those with delayed excretion have an increasing risk of adverse drug reactions.