Methotrexate: Effective against Rheumatism and Cancer

Methotrexate (MTX) is used to treat chronic inflammatory diseases such as rheumatism, psoriasis, and Crohn’s disease. In high doses, it can also be used as part of chemotherapy to treat leukemia and other cancers. The active ingredient inhibits an enzyme in folic acid metabolism, thus interfering with the division of cancer cells and cells of the immune system that require folic acid for growth. As a result, treatment with methotrexate can have significant side effects: Gastrointestinal problems are common. In addition, skin rashes and itching may occur, as well as liver and kidney damage.

Effect of methotrexate

Methotrexate belongs to a group of drugs called cytostatics and inhibits cell division in the body in the following way: For a cell to divide, it needs folic acid. The chemical structure of methotrexate is very similar to folic acid. As a result, methotrexate “fits” into an enzyme that normally provides folic acid to the cell in the form it needs and blocks it. As a result, not enough folic acid is available to the cell and cell division is prevented. Thus, on the one hand, methotrexate is effective against cancer because it prevents the growth of tumor cells. On the other hand, it can be used against chronic inflammatory diseases, because in these so-called autoimmune diseases the immune system fights cells of its own body. In this case, methotrexate prevents the immune cells from multiplying as much and thus slows down the course of the disease. However, the division of other cells in the human body is also slowed down, which is why numerous side effects can occur during use. Recognize psoriasis: these pictures help!

Application and dosage

In rheumatoid therapy, the dosage ranges from 7.5 to 20 milligrams per week. In the treatment of psoriasis, the maximum dose is 30 milligrams, taken once a week as a tablet. If methotrexate is used to treat Crohn’s disease, a chronic inflammatory bowel disease, 15-25 milligrams are administered once a week as an injection. In cancer therapy, methotrexate slows the growth of tumor cells. Considerably higher doses are used here, which are calculated per square meter of body surface. Depending on the type of disease, the maximum dose is up to 12,000 mg/m². In this case, a so-called rescue therapy must be carried out: An infusion of folic acid is supplied to alleviate the side effects.

Side effects of methotrexate

Methotrexate mainly affects cancer cells and cells of the immune system because they divide particularly quickly. Nevertheless, to a lesser extent, other cells of the body are also affected in their multiplication, which is why there can sometimes be severe side effects while taking the drug. Among the most common problems when taking methotrexate are complaints in the gastrointestinal tract such as nausea, vomiting and diarrhea. In addition, inflammation of the mucous membranes in the mouth and throat may occur, as well as skin rashes, itching, and hypersensitivity to light. Occasionally, there is an increase in connective tissue in the lungs (pulmonary fibrosis) or inflammatory changes (pneumonitis). In addition, the suppression of the immune system increases susceptibility to infections and the risk of benign and malignant tumor formation. Especially at high doses in cancer therapy, kidneys and liver can be damaged. For a complete list of methotrexate side effects, take a look at the package insert.

Contraindications to methotrexate

Just like other agents, methotrexate has a number of contraindications. For example, it should not be used if there is hypersensitivity to the active ingredient, or if you have any of the following pre-existing conditions:

  • Renal dysfunction
  • Liver disease
  • Diseases of the bone marrow
  • Immunodeficiency (AIDS)
  • Ulcers in the gastrointestinal tract
  • Infections
  • Alcohol dependence

Similarly, treatment with methotrexate should not be given during pregnancy and lactation.

Possible interactions

The use of methotrexate may interact with many other drugs.For example, the risk of kidney damage may be increased if anti-inflammatory painkillers (non-steroidal anti-inflammatory drugs, NSAIDs) such as ASA, ibuprofen or diclofenac are taken at the same time, as these active ingredients are also excreted via the kidneys. If these painkillers are combined with methotrexate in rheumatism therapy, for example, close medical monitoring must therefore take place. Some medicines such as the gout medicine probenecid and some antibiotics such as penicillins, sulfonamides, tetracyclines, and chloramphenicol affect the absorption, metabolism, or excretion of methotrexate and may thus unintentionally alter the level of active substance in the blood. Therefore, always inform your doctor about all medications you are taking before starting treatment! Please refer to the package insert for a complete list of drug interactions.

Methotrexate and alcohol

Alcohol consumption during therapy with methotrexate increases the risk of liver damage and other adverse effects. As with many other agents, you should therefore avoid drinking alcohol during treatment with methotrexate. Excessive consumption of caffeinated beverages such as coffee, cola, and black tea should also be avoided.

Methotrexate in pregnancy

Methotrexate should not be used during pregnancy because it damages genetic material and may cause miscarriage and severe developmental problems in the unborn child. Therefore, during treatment and for six months thereafter, women and men of sexually mature age should use reliable contraception. If you wish to have a child, inform your doctor before treatment. Because the active ingredient passes into breast milk, methotrexate should not be taken even if you are breastfeeding.