Methotrexate (MTX) is a chemotherapy agent and immunosuppressant used to treat a variety of medical conditions, including cancer, autoimmune diseases, and inflammatory disorders. It works by inhibiting the enzyme dihydrofolate reductase, which is essential for DNA synthesis. This inhibition disrupts cell division and proliferation, effectively treating rapidly dividing cells such as cancer cells. Methotrexate is also used in lower doses to manage conditions like rheumatoid arthritis, psoriasis, and Crohn’s disease by modulating the immune system to reduce inflammation and immune system activity. The test measures the concentration of the drug in the blood to ensure therapeutic levels are maintained, minimize toxicity, and assess the need for dosage adjustments.
Measuring serum methotrexate levels is essential in clinical practice, especially in patients undergoing high-dose methotrexate therapy for cancer treatment. Since methotrexate is metabolized and eliminated by the kidneys, its serum levels can provide critical information regarding the effectiveness of the treatment and the risk of adverse effects, particularly nephrotoxicity and hepatotoxicity. Monitoring methotrexate levels is essential to avoid side effects such as mucositis, bone marrow suppression, and liver damage, which can occur when drug concentrations exceed safe levels.
The test for methotrexate is typically ordered during cancer treatments, such as in cases of leukemia, lymphoma, or osteosarcoma, where high doses of the drug are used in combination with other chemotherapy agents. It is crucial to monitor methotrexate levels in these settings due to the narrow therapeutic window of the drug, meaning that the difference between an effective dose and a toxic dose can be slight. This necessitates frequent testing during and after drug administration, as methotrexate can remain in the body for an extended period, even after treatment has concluded.
Lower doses of methotrexate are often prescribed for patients with autoimmune diseases, and serum levels are monitored to ensure that the drug is effective in controlling the disease and safe with minimal adverse effects. Patients with pre-existing kidney or liver conditions need regular methotrexate serum tests, as these organs are involved in drug metabolism and excretion.
