See the DrugPatentWatch profile for methotrexate

Methotrexate is a medication used to treat certain types of cancer, rheumatoid arthritis, and severe psoriasis in both adults and children. It can interact with other medications, which can affect how well they work or increase the risk of side effects. However, there is limited information specifically about how methotrexate affects other medications in children.

Methotrexate can increase the levels of certain medications in the body by decreasing the activity of enzymes that break down these drugs. For example, methotrexate can increase the levels of the antibiotic trimethoprim-sulfamethoxazole (Bactrim, Septra) and the antifungal medication fluconazole (Diflucan) [1]. This can increase the risk of side effects from these medications.

Methotrexate can also decrease the levels of certain medications in the body by increasing the activity of enzymes that break down these drugs. For example, methotrexate can decrease the levels of the anticonvulsant medication phenytoin (Dilantin) [1]. This can make the anticonvulsant medication less effective at preventing seizures.

In addition, methotrexate can interact with medications that affect the immune system. For example, methotrexate should not be used with other medications that weaken the immune system, such as biologic response modifiers (e.g., adalimumab, etanercept), because of an increased risk of infection [2].

It is important to tell your child's healthcare provider about all the medications they are taking, including prescription and over-the-counter drugs, vitamins, and herbal supplements. This will help the healthcare provider to determine if there are any potential drug interactions and to adjust the treatment plan accordingly.

Sources:

1. Methotrexate. (2021). In Mayo Clinic Drug Monographs [Internet]. Mayo Foundation for Medical Education and Research; 2021. Available from: https://drug-monographs.mayoclinic.org/drug-monographs/methotrexate.html
2. Methotrexate. (2021). In Lexicomp Online [Internet]. Hudson, OH: Wolters Kluwer Health; 2021. Available from: https://online.lexi.com/lco/action/doc/retrieve/docid/patch_f/7315
3. Drug Interactions: What You Should Know. (2020). In U.S. Food and Drug Administration. Available from: https://www.fda.gov/drugs/resources-information-approved-drugs/drug-interactions-what-you-should-know
4. Methotrexate. (2021). In DrugPatentWatch. Available from: https://www.drugpatentwatch.com/drugs/methotrexate