Methotrexate injections can be fatal in certain people, so doctors typically restrict the use of the drug to patients with potentially deadly diseases or diseases that are not treatable with safer drugs. Some cancers, such as breast cancer, bone cancer and leukemia, may be controlled by a methotrexate injection course. Psoriasis and arthritis are examples of non-lethal conditions that may also respond to the drug.
The way a methotrexate injection works in the body is to interfere with cell growth and division. It does this by blocking the action of an enzyme called dihydrofolic acid reductase. This enzyme works in an important step in which the building blocks of nucleic acids are made. New cells cannot grow without new nucleic acids, and so cell growth stops.
This ability of methotrexate may be useful for people with certain cancers. The drug may not be able to reverse the uncontrolled growth of cells that is a feature of cancer, but it can stop the growth and prevent the cancer getting worse. Breast cancer, leukemia and the bone cancer osteosarcoma can respond well to a methotrexate injection regimen. Trophoblastic neoplasms, such as some skin cancers, and a lymphoma called mycosis fungoides, can also undergo treatment with a methotrexate injection course. Tumors that grow as solid cancers may also be suitable for treatment with the drug.
As these cancers can be life-threatening, the potential benefits of methotrexate may outweigh the risks of the drug. The drug can cause cancer itself, in the form of lymphoma. It can also affect function of organs like the liver, lungs and digestive tract, to such an extent that the damage is fatal. The medicine can also result in dangerous skin reactions, or increase the likelihood of serious lung infections.
A long list of potential side effects make the drug unsuitable for most medical conditions. Some conditions, however, that do not place the life of the patient at risk, but severely affect everyday life, may necessitate methotrexate treatment. Certain chronic medical problems, like rheumatoid arthritis or psoriasis, may not respond to safer treatments.
In this situation, a patient may prefer to take the risk of the methotrexate side effects against the possibility of a successful treatment. Psoriatic arthritis, a form of arthritis that displays both skin symptoms and joint issues, is another condition that a doctor may prescribe the medicine for. Methotrexate is not a cure for these diseases, but can control the symptoms.