Methotrexate and Sulfamethoxazole and trimethoprim interaction
Methotrexate and Sulfamethoxazole and trimethoprim: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Methotrexate (Xatmep) label · effective 2026-05-28
Trimethoprim/sulfamethoxazole has been reported to increase bone marrow suppression in patients receiving methotrexate.
From the Sulfamethoxazole and trimethoprim (SULFATRIM) label · effective 2026-01-05
Sulfonamides can also displace methotrexate from plasma protein binding sites and can compete with the renal transport of methotrexate, thus increasing free methotrexate concentrations.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.