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What is Methotrexate? How does methotrexate work?
Methotrexate (formerly known as amethopterin) is a medication used to treat a wide range of medical conditions including blood and solid organ cancers, autoimmune conditions, ectopic pregnancy, and in some cases, medical abortions.[1]
Brand names that are associated with this medication are:
Trexall
Rasuvo
Methotrexate works by inhibiting dihydrofolate acid reductase, an enzyme that makes folic acid and is required for cells to divide, as well as make, recycle and repair their DNA.[2] This enzyme is especially important for the survival of rapidly dividing cells like cancer cells and certain immune cells such as T-cells and B-cells. Therefore, methotrexate can treat cancers, as well as autoimmune and autoinflammatory conditions where the immune system is dysregulated and working abnormally.
Methotrexate is FDA-approved to treat psoriasis (both skin and joint diseases), rheumatoid arthritis, Sezary Syndrome (a blood cancer that originates from the skin lymphoma called cutaneous T-cell lymphoma), lung cancer (particularly squamous cell and small cell types), Non-Hodgkin’s lymphoma, and cancers related to pregnancy (gestational choriocarcinoma, chorioadenoma destruens and hydatidiform mole).[3]
Methotrexate is often used off-label by physicians for a large number of other skin conditions including immunobullous diseases, autoimmune connective tissue diseases, vasculitis, (inflammation of the blood vessels) and eczema.[1]
Methotrexate tablets can be taken orally, or solution forms can be administered intravenously (into veins), intramuscularly (into the muscle), or subcutaneously (under skin).[1] When taken orally, it must first be absorbed by the intestines, then passed through the liver before reaching the bloodstream. Therefore, the bioavailability of the drug is lowered.[3] However, when administered by injection, the entire dose of methotrexate is absorbed directly into the blood, which is called 100% bioavailability.
Methotrexate is often administered once weekly. Since methotrexate inhibits the synthesis of folate, an important vitamin for cellular function, folic acid supplementation is usually taken daily, except on the day that the methotrexate dose is taken.[1]
A practitioner should periodically monitor liver, kidneys, and blood count of a patient who is taking methotrexate.