Why is Methotrexate prescribed?
Methotrexate is an anticancer drug used in the treatment of lymphoma (cancer of the lymph nodes) and certain forms of leukemia. It is also given to treat some forms of cancers of the uterus, breast, lung, head, neck, and ovary. Methotrexate is also given to treat rheumatoid arthritis when other treatments have proved ineffective, and is sometimes used to treat very severe and disabling psoriasis (a skin disease characterized by thickened patches of red, inflamed skin often covered by silver scales).
Most important fact about Methotrexate
Be certain to remember that in the treatment of psoriasis and rheumatoid arthritis, methotrexate is taken once a week, not once a day. Accidentally taking the recommended weekly dosage on a daily basis can lead to fatal overdosage. Be sure to read the patient instructions that come with the package.
How should you take Methotrexate?
Take methotrexate exactly as prescribed, and promptly report to your doctor any new symptoms that may develop.
Methotrexate is given at a higher dosage for cancer than for psoriasis or rheumatoid arthritis. After high-dose methotrexate treatment, a drug called leucovorin may be given to limit the toxic effects.
--If you miss a dose...
Skip it and go back to your regular schedule. Do not take 2 doses at once.
--Storage instructions...
Store at room temperature, away from light.
What side effects may occur?
Side effects cannot be anticipated. If any develop or change in intensity, inform your doctor as soon as possible. Only your doctor can determine whether it is safe for you to continue taking methotrexate.
• More common side effects may include:
Abdominal pain and upset, chills and fever, decreased resistance to infection, dizziness, fatigue, general feeling of illness, mouth ulcers, nausea
If you are taking methotrexate for psoriasis, you may also experience hair loss and/or sun sensitivity, and your patches of psoriasis may give a burning sensation.
Methotrexate can sometimes cause serious lung damage that makes it necessary to limit the treatment. If you experience a dry cough, fever, or breathing difficulties while taking methotrexate, be sure to tell your doctor right away.
During and immediately after treatment with methotrexate, fertility may be impaired. Men may have an abnormally low sperm count; women may have menstrual irregularities.
People on high doses of methotrexate may develop a brain condition signaled by confusion, partial paralysis, seizures, or coma.
Why should Methotrexate not be prescribed?
Do not take Methotrexate if you are sensitive to it or it has given you an allergic reaction.
Do not take Methotrexate if you are pregnant.
Methotrexate treatment is not suitable for you if you suffer from psoriasis or rheumatoid arthritis and also have one of the following conditions:

Abnormal blood cell count
Alcoholic liver disease or other chronic liver disease
Alcoholism
Anemia
Immune-system deficiency
Special warnings about Methotrexate
Before you start taking methotrexate, your doctor will do a chest X-ray plus blood tests to determine your blood cell counts, liver enzyme levels, and the efficiency of your kidney function. While you are taking methotrexate, the blood tests will be repeated at regular intervals; if you develop a cough or chest pain, the chest X-ray will be repeated.
If you are being treated for psoriasis or rheumatoid arthritis, your doctor will test your liver function at regular intervals. You should avoid alcoholic beverages while taking Methotrexate.
You may develop an opportunistic infection--one that takes advantage of your altered body chemistry--while you are taking methotrexate. Before receiving an immunization or vaccination, be sure to inform health care workers that you are taking Methotrexate.
Older or physically debilitated people are particularly vulnerable to toxic effects from methotrexate. Your doctor will prescribe methotrexate with great caution if you have any of the following:

Active infection
Liver disease
Peptic ulcer
Ulcerative colitis
Possible food and drug interactions when taking Methotrexate
If you are being given methotrexate for the treatment of cancer or psoriasis, you should not take aspirin or other nonsteroidal painkillers such as Advil or Naprosyn; this combination could increase the toxic effects of methotrexate. If you are taking methotrexate for rheumatoid arthritis, you may be able to continue taking aspirin or a nonsteroidal painkiller, but your doctor should monitor you carefully.
Other drugs that may increase the toxic effects of methotrexate include:

Cisplatin (Platinol)
Penicillins
Phenylbutazone
Phenytoin (Dilantin)
Probenecid
Retinoid drugs such as Retin-A and Renova
Sulfa drugs such as Bactrim and Gantrisin
Sulfa drugs may increase methotrexate's toxic effect on the bone marrow, where new blood cells are made.
Certain antibiotics, including tetracycline (Sumycin) and chloramphenicol (Chloromycetin), may reduce the effectiveness of methotrexate. This is also true of vitamin preparations that contain folic acid.
In addition, methotrexate can alter the effect of theophylline (Quibron, Theo-Dur).
Special information if you are pregnant or breastfeeding
A woman should not start methotrexate therapy until the doctor is sure she is not pregnant. Because methotrexate causes birth defects and miscarriages, it must not be taken during pregnancy by women with psoriasis or rheumatoid arthritis. It should be taken by women being treated for cancer only if the potential benefit outweighs the risk to the developing baby. In fact, a couple should avoid pregnancy if either the man or the woman is taking methotrexate. After the end of methotrexate treatment, a man should wait at least 3 months, and a woman should wait for the completion of at least one menstrual cycle, before attempting to conceive a child.
Methotrexate should not be taken by a woman who is breastfeeding; it does pass into breast milk and may harm a nursing baby.
Recommended dosage
Treatment with methotrexate is highly individualized. Your doctor will carefully tailor your dosage of methotrexate in order to avoid serious side effects and possible under- or overdosing.
Overdosage
Taken in excess, methotrexate can cause serious and even fatal damage to the liver, kidneys, bone marrow, lungs, or other parts of the body. Symptoms of overdosage may include lung or breathing problems, mouth ulcers, or diarrhea. Initially, however, serious damage caused by methotrexate may be apparent only in the results of blood tests. For this reason, careful, regular monitoring by your doctor is necessary. If for any reason you suspect symptoms of an overdose of Methotrexate, seek medical attention immediately.