Methotrexate.
Last updated Friday, February 11, 2005
Dosage & precautionsCommon dosage 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. Toxicity 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.Interactions 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.
Precautions 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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