Methotrexate is a competitive inhibitor of dihydrofolate reductase, an enzyme responsible for tetrahydrofolate (THF) regeneration. 5,10-methylenetetrahydrofolate, formed from THF, is essential for the de novo synthesis of the nucleotide thymidine, required for DNA synthesis.
Methotrexate therefore inhibits the synthesis of DNA, RNA, thymidylates and proteins, and is used as an anti-cancer treatment.
Patients on high dose methotrexate infusion.
SST (gold top), serum (red top), or EDTA (lavender top)
Up to 6 weeks
Not currently performed in house; this is a referred test.
Please state the date and time of the last dose of methotrexate.