Enzyme Homogeneous Competitive Immunoassay
Monitor therapeutic drug level, evaluate potential toxicity
A therapeutic range for Methotrexate has not been defined. No precise relationship between methotrexate serum levels and antineoplastic efficacy has been established. Serum concentrations are monitored during high-dose therapy to identify the time when active intervention by leucovorin rescue should be initiated. Serum concentrations indicative of an increased risk of toxicity after a 4-6 hour high-dose infusion are as follows:
24 hr >5.00 umol/L
48 hr >0.50 umol/L
72 hr >0.10 umol/L
Collect blood in a red top or green top tube; do not use SST tube. Centrifuge, aliquot serum into a plastic vial, and refrigerate. Cerebrospinal fluid is also an acceptable specimen.