methotrexate, Rheumatrex, Trexall

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GENERIC NAME: methotrexate

BRAND NAMES: Rheumatrex, Trexall

DRUG CLASS AND MECHANISM: Methotrexate is classified as an antimetabolite drug which means it is capable of blocking the metabolism of cells. (Metabolism consists of the production and destruction of important components of the cell as well as the production of energy for use by the cell.) As a result of this effect, it has been found helpful in treating certain diseases associated with abnormally rapid cell growth, such as cancer of the breast and psoriasis. Recently, methotrexate has been shown to be effective in inducing miscarriage, for example in patients with ectopic pregnancy. This effect of methotrexate is attributed to its action of killing rapidly growing cells such as those of the placenta. It also has been found very helpful in treating rheumatoid arthritis, although its mechanism of action in this illness is not known. It seems to work, in part, by altering immunity which may play a role in causing rheumatoid arthritis. The FDA approved methotrexate in December 1953.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS: Injectable: 25 mg/ml. Powder for injection: 1 g. Tablet: 2.5, 5, 7.5, 10 and 15 mg

STORAGE: Methotrexate should be stored at room temperature 15 C to 30 C (59 F to 86 F), avoiding light.

PRESCRIBED FOR: Methotrexate is used for cancer treatment at higher doses than for other uses and is often administered intravenously or intramuscularly. Methotrexate is used to treat psoriasis, an inflammatory skin disease, as well as the arthritis that occurs in 10 percent of these patients (psoriatic arthritis). It also is used to treat active rheumatoid arthritis in adults and children and other rheumatic diseases, including polymyositis and systemic lupus erythematosus. Methotrexate has been used to induce miscarriage in patients with ectopic pregnancies.

DOSING: Methotrexate may be taken with or without food. For rheumatoid arthritis and psoriasis, the dose of methotrexate is given weekly, by injection or orally. The oral dose is 7.5 to 20 mg once weekly. For psoriasis, the starting oral dose is a single 7.5 mg dose weekly or 2.5 mg every 12 hours for three doses, once weekly. The final dose ranges between 10 and 25 mg weekly orally or by injection.

DRUG INTERACTIONS: Using nonsteroidal anti-inflammatory drugs (NSAIDs) before or during methotrexate treatment may result in serious adverse events because NSAIDS may increase the blood concentrations of methotrexate. Combining methotrexate with drugs that adversely affect the liver or kidneys may result in additional liver or kidney toxicity.

Combining methotrexate with trimethoprim/sulfa-methoxazole may increase the risk of bone marrow toxicity.

Penicillins may increase blood concentrations of methotrexate leading to increased side effects of methotrexate.

Toxic effects on the liver increase when methotraxate is combined with other drugs that affect the liver.

PREGNANCY: Methotrexate should not be used in pregnancy, as it can be toxic to the embryo and can cause fetal defects and spontaneous abortion (miscarriage). It should be discontinued prior to conception if used in either partner. Male patients should stop taking methotrexate at least 3 months prior to a planned conception in order to avoid the theoretical risk of methotrexate-induced abnormal sperm. Women should discontinue use for at least one ovulatory cycle before conception to reduce exposure of a developing ovarian follicle to methotrexate.




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