Caution with methotrexate dosing in autoimmune disease.
Methotrexate (MTX) is used to treat severe forms of psoriasis, autoimmune diseases (e.g., rheumatoid arthritis), and various tumor diseases. It is strictly available only on prescription.
As a so-called "antimetabolite", the active ingredient methotrexate inhibits the formation of certain building blocks of the DNA of the cell nucleus and thus actively intervenes in their synthesis and repair as well as in cell division. Cells that divide very rapidly, such as tumor cells or epithelial cells of the skin, whose division rate in psoriasis is greatly increased compared to normal skin, react to this effect first and foremost.
Since the hematopoietic system of the human body also has a high cell division rate, therapy with MTX is associated with the risk of a reduced number of white blood cells (important for immune defense) or platelets (important for blood clotting). This can lead to the occurrence of infections or bleeding, which in rare cases can be fatal if not detected and treated in time.
Therefore, in order to avoid overdoses, dosage and intake intervals must be strictly adhered to:
- In autoimmune diseases such as dermatological diseases (e.g., psoriasis) and rheumatological diseases (e.g., rheumatoid arthritis), methothrexate may be taken only once a week on the day specified by the physician.
- To improve tolerability of the drug, the weekly dose may be divided into three parts and swallowed with a little water at intervals of twelve hours, spread over one day of the week.
- In no case should the intake be continued daily!
