What is methotrexate, and how does it work (mechanism of action)?

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.

What brand names are available for methotrexate?

Otrexup, Rasuvo

Is methotrexate available as a generic drug?

GENERIC AVAILABLE: Yes

Do I need a prescription for methotrexate?

Yes

What are the side effects of methotrexate?

Methotrexate can cause severe toxicity which usually is related to the dose taken. The most frequent reactions include:

• mouth sores,
• stomach upset;
• low white blood counts;
• severe toxicity of the liver, kidneys and bone marrow, which require regular monitoring with blood tests;
• headache
• drowsiness

Methotrexate can cause itching, skin rash, dizziness, and hair loss. A dry, non-productive cough can be a result of rare lung toxicity.

What is the dosage for methotrexate?

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.

Is methotrexate safe to take if I'm pregnant or breastfeeding?

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.

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

What else should I know about methotrexate?

What preparations of methotrexate are available?

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

How should I keep methotrexate stored?

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