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HomeAbout MethotrexateDosage & precautionsCommon dosageToxicityInteractionsPrecautionsSide effectsDeciding to start Methotrexate

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Methotrexate.

Last updated Friday, February 11, 2005

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Dosage & precautions

What are the common dosage amounts for methotrexate?

Methotrexate is taken once a week, either orally (as pills) or by injection. The tablet strength is 2.5 milligrams, and the starting dose is usually three pills (7.5 milligrams) taken one day a week. The dose may be increased over time if there is no initial benefit. Generally, doses between 7.5 and 20 milligrams one day a week are used to treat rheumatoid arthritis. Doses higher than 20 milligrams weekly may occasionally be used.

If taken orally, methotrexate may be taken all in one dose or split up and taken two or three times over a 24-hour period, once a week. For example, you can take it all on Monday morning or on Monday morning, Monday evening, and finally on Tuesday morning. It may also be given injection either just under the skin, in the muscle, or directly into the vein. Injections may be recommended for people who are not responding to oral methotrexate or are developing intestinal side effects such as nausea.

What is the maximum dosage of methotrexate?

Methotrexate should not be taken more often than one 24-hour period per week, and should be taken on the same day each week. More frequent administration can be associated with serious side effects. Mark a calendar to remind yourself when to take your dose. If you become confused about when to take the drug, call your doctor to clarify the situation before you take the next dose.

Does methotrexate interact with any other drugs?

Whenever a new medication is recommended, consult your doctor to make sure there is no problem taking it with methotrexate. You should not take the antibiotic trimethoprim/sulfamethoxazole (Bactrim or Septra) with methotrexate. In some people, a shortage of folic acid can occur with methotrexate therapy. Therefore, your doctor may prescribe supplemental folic acid pills.

Are there any warnings about methotrexate for children or pregnant women or nursing mothers?

Children

Frequently children with juvenile rheumatoid arthritis and related forms of pediatric arthritis are also commonly treated with methotrexate, usually by mouth, but occasionally by intramuscular or intravenous injection. The side effects are similar in children and adults. Dosages of methotrexate for children are calculated by body weight or body surface area and are then adjusted as the child grows. Methotrexate treatment for children with arthritis may help them more easily attend school, achieve normal stature, and reach other age-appropriate developmental milestones.

Even though methotrexate has not yet received approval from the U.S. Food and Drug Administration for use in JRA, it is being used widely by arthritis specialists to treat this disease.

Pregnant or nursing mothers

Methotrexate may cause birth defects if taken by a woman at the time of conception or during pregnancy. Women of childbearing potential must use birth control and must not get pregnant while receiving methotrexate. After methotrexate treatment is stopped, women should wait at least one menstrual cycle before trying to conceive. Methotrexate has no effect on fertility, and if the drug is stopped at least 30 days prior to attempting conception, there will be no effect on the unborn child.

Breast-feeding is not recommended while taking methotrexate, because the medicine may be passed to the child through the mother's milk.


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