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.
NURSING MOTHERS: Methotrexate is excreted in breast milk and should not be used by nursing mothers.
Medically reviewed by Eni Williams, PharmD
Reference: FDA Prescribing Information
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