Methotrexate

Brand names

• Abitrexate
• Folex
• Folex PFS
• Methotrexate
• Mexate
• Mexate AQ
• Rheumatrex Dose Pack

Usage

To treat certain kinds of cancer, psoriasis, and rheumatoid arthritis.

How it works

Methotrexate interferes with the activity of an enzyme needed for the maintenance and replication of cells, especially those that divide and proliferate rapidly. Such cells include many types of cancer cells, as well as those that compose the bone marrow and the cells that line the mouth, intestine, and bladder. Consequently, in addition to its cancer-fighting effects, methotrexate may also harm healthy tissues in the body, causing unpleasant or serious side effects. It is unknown how methotrexate works to ease rheumatoid arthritis, but it appears to modify the function of the immune system, whose activity is believed to play a role in the progression of the disease.

Side effects

Serious

Black, tarry stools; bloody vomit; diarrhea; flushing or redness of skin; sores in mouth and on lips; stomach pain; blood in urine or stools; confusion; seizures; cough or hoarseness; fever or chills; pain in lower back or side; painful or difficult urination; red spots on skin; shortness of breath; swollen feet or lower legs; unusual bleeding or bruising; back pain; dark urine; drowsiness; dizziness; headache; joint pain; unusual fatigue; yellow-tinged eyes or skin.

Common

Loss of appetite, nausea and vomiting, minor mouth ulcers.

Less common

Acne, boils, pale skin, skin rash, or itching.

Possible interactions

Other medicaments:

Methotrexate may decrease the effects of:

• digoxin (Lanoxin).
• folate (various) by blocking the change (conversion) of folate to folic acid.
• phenytoin (Dilantin) or fosphenytoin (Cerebyx).

The following medicaments may increase the effects of methotrexate and enhance its toxicity:

• aspirin and other salicylates.
• NSAIDs.
• omeprazole (Prilosec).
• probenecid (Benemid).
• rofecoxib (VIOXX).

Methotrexate taken concurrently with:

• amiodarone (Cordarone) may result in methotrexate toxicity.
• bismuth subsalicylate (Pepto-Bismol, others) may result in methotrexate toxicity.
• carbenicillin (Geocillin, others) and other penicillins may lead to methotrexate toxicity.
• cholestyramine (Questran, others) and other cholesterol-lowering resins may result in decreased methotrexate effectiveness.
• cotrimoxazole (Bactrim) may result in lowering of all blood cells (pancytopenia).
• cyclosporine (Sandimmune) can result in increased toxicity from both medicaments. This combination should be avoided.
• etretinate (Tegison) results in increased liver toxicity.
• influenza vaccine (flu) may blunt benefits of the vaccine.
• live-virus vaccines (such as RotaShield) may lead to severe infections.
• pneumococcal or smallpox vaccine may result in decreased immune response to the vaccine.
• sulfa medicaments, such as sulfamethoxazole, can result in increased hematological toxicity.
• tamoxifen (Nolvadex) may increase risk of blood clots (thromboembolism)-part of a combination regimen that leads to this.
• thiazide diuretics may increase risk of myelosuppression.
• theophylline (Theo-Dur, others) may result in theophylline toxicity; decreased theophylline doses may be needed.
• triamterene (Dyazide, others) may increase risk of bone marrow problems (myelosuppression).
• trimethoprim (Septra, others) may increase risk of toxicity.
• yellow fever vaccine can result in blunted response and benefit from the vaccine.

Foods:

Avoid highly seasoned foods that could be irritating. Between courses of treatment, eat liberally of the following foods: beef, chicken, lamb and pork liver, asparagus, navy beans, kale and spinach. Any food will reduce the peak methotrexate level obtained. Folic acid supplementation is suggested for people who will take this medicine on an ongoing basis.

Herbal medicines or minerals:

Some patients use Echinacea to attempt to boost their immune systems. Unfortunately, use of Echinacea is not recommended in people with damaged immune systems (even if a medicine caused the damage). This herb may also actually weaken any immune system if it is used too often or for too long a time. Like methotrexate, St. John's wort may cause sensitivity to the sun. Avoid this combination.

Alcohol:

Avoid completely.

Marijuana smoking:

May cause additional impairment of immunity.

Exposure to sun:

Use caution-this medicament can cause photosensitivity. Avoid ultraviolet lamps.

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