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By A. G. Moore

Methotrexate is an immunosuppressive drug—which means it interferes with the production of some kinds of immune cells. Back in the 1950’s doctors noticed that patients who had certain types of cancer did better if they were deficient in folic acid. This observation led to the development of methotrexate, which interferes with the action of folic acid. Treatment with methotrexate became common for selected cancers because the medicine was found to have less side effects than some other preparations.

Eventually, methotrexate was discovered to be useful in suppressing immune activity in autoimmune diseases, especially rheumatoid arthritis, but also lupus and Crohn’s disease, among others. Doses necessary to achieve a therapeutic effect in lupus are much lower than those administered in the treatment of cancer. Consequently, side effects may not be as severe.

However, methotrexate is a powerful drug and can have very serious side effects. It is absolutely prohibited if there is a chance of pregnancy. Even after discontinuing use of the drug, pregnancy must be delayed until all of the medicine has cleared from the system. Among the many serious side effects that may occur as a result of taking methotrexate are liver damage, lung damage, and nervous system complications.

Drug interactions include penicillins, probenecid, phenobarbitol, carbamazepine, Bactrim and NSAIDs (although NSAIDs may sometimes be prescribed in combination with methotrexate). It is recommended that while on Methotrexate the patient abstain from drinking because of possible damage to the liver. It is essential that the patient be monitored (blood tests) regularly. Any sign of shortness of breath or chest discomfort should be reported immediately to the doctor.

Patients taking methotrexate often are prescribed a folic acid supplement to avoid deficiency.

Though Methotrexate is widely used for the treatment of lupus, it is generally not the medicine of choice for those who have lupus nephritis or organ involvement. According to the Mayo Clinic, methotrexate should be used with caution in lupus patients with these symptoms.

While methotrexate is a powerful drug and can have potentially serious side effects, the fact remains that it has been very useful in the treatment of a variety of diseases. As with every medicine, risk has to weighed against benefit. For many patients, the benefits are greater than the risk.

Sources for further reading:

*American College of Rheumatology: Methotrexate.

*MedlinePlus: Methotrexate

*DermNet NZ: Methotrexate

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