| OBJECTIVES: To improve the effect and safety of high dose methotrexate (HD-MTX) chemotherapy, the metabolic regularity of MTX and its clinical application were discussed. METHODS: 67 acute lymphoblastic leukemia children received HD-MTX (1.0-4.0 g.m-1) treatment were involved in this study. The serum samples were collected at different time during 0.5h-68h(or 91h) after infusion started. The effect of treatment were evaluated according to MTX concentration in 12h. The calcium folinate rescue schem were determined with the result of MTX serum concentration in terminal elimination phase. The adverse reaction of all cases were also monitored to evaluate the remedy safety. RESULTS: The MTX serum concentration of each cases showed falling sharply in initial elimination phase, declining mildly in terminal phase and great imparity at the same time among individuals. When MTX dosage of 12 patients increased from 3.0g.m-1 to 4.0g.m-1, the serum concentrations in 0.5h, 12h and 24h increased significantly (p<0.05), while the concentrations in 73h, 91h and drug adverse reaction incidence of the two dosage groups have no significant difference(p>0.05) . More than 90% cases treated with 3.0g.m-1 and 4.0g.m-1 dosage could maintain their serum concentration in 12 hour over the 2×10-5mol.L-1 penetrating concentration. Only one patient was observed with large area skin and oral mucosa being impaired, and no severe irreversible adverse reaction occurred. CONCLUSIONS: Within a dosage extent, the MTX serum concentration of the initial phase(0h-12h) increased while MTX dosage added, but the concentration of the terminal phase(after 44h) showed no such correlation with MTX dosage,and it should be taken more care about in the therapeutic drug monitoring. MTX serum concentration monitoring is very useful for controlling the rescuing time and dosage rationally to add the MTX dosage to the extent that can be tolerated by ALL children.
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