Analysis index

1 ml serum

Therapeutic drug monitoring

< 5.0 µmol/l after 24 hours

< 0.5 µmol/l after 48 hours

< 0.05 µmol/l after 72 hours    

High dose:

< 10.0 µmol/l after 24 hours

< 1.0 µmol/l after 48 hours

< 0.1 µmol/l after 72 hours

Methotrexate (MTX) is used in cancer therapy and in significantly lower doses for the treatment of various autoimmune processes (especially rheumatoid arthritis). It is a folic acid analogue, which competitively inhibits the dihydrofolate reductase. This means, that less tetrahydrofolic acid is available for the biosynthesis of nucleobases, which leads to an inhibition of cell proliferation (cytostatic effect). The antirheumatic effect of MTX is not yet fully clarified with regard to its mechanism, and is only based partially on its inhibiting effect to the lymphocyte proliferation. Common side effects are (depending on dosage) nausea, hepatotoxicity, stomatitis, hair loss and bone marrow suppression with megaloblastic anemia. The non-desired effects can be reduced considerably by adjuvant supplementation with high-dose folic acid 24 – 48 hours after MTX administration.

Caution: Due to its teratogenic effect, MTX must not be used during pregnancy or if the patient desires to have children (Methotrexate embryopathy)!

Labor Zentrum Weser Prof. Dr. med. Schmitz Minden