Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

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 the rapidly growing cells of the placenta. It has also 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.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

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

STORAGE: Store at room temperature 15° to 30°C (59° to 86°F), avoid light.

PRESCRIBED FOR: Methotrexate is used for cancer treatment generally in 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 is also 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.

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.

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.

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 and females should discontinue use for at least one ovulatory cycle before conception.

NURSING MOTHERS: Methotrexate is excreted in breast milk and should not be used by nursing mothers.

SIDE EFFECTS: Methotrexate can be well tolerated, but also can cause severe toxicity which is usually related to the dose taken. The most frequent reactions include mouth sores, stomach upset, and low white blood counts. Methotrexate can cause severe toxicity of the liver, kidneys and bone marrow, which require regular monitoring with blood tests. It can cause headache and drowsiness which may resolve if the dose is lowered. Methotrexate can cause itching, skin rash, dizziness, and hair loss. A dry, non-productive cough can be a result of rare lung toxicity.

Reference: FDA Prescribing Information