Common interactions: what methotrexate can react with
Methotrexate interacts with several drug classes that can increase toxicity (especially to the blood and liver) or change methotrexate levels in the body. The most important interactions typically involve:
NSAIDs (including aspirin and ibuprofen)
NSAIDs can raise methotrexate levels and increase the risk of side effects, including low blood counts and kidney-related toxicity, particularly in higher doses or in people with reduced kidney function.
Blood thinners (warfarin and similar anticoagulants)
Methotrexate can increase bleeding risk in some patients by affecting blood clotting control and/or the effects of anticoagulants. INR and bleeding symptoms may require closer monitoring.
Antibiotics that affect gut bacteria or kidney handling (e.g., TMP-SMX)
Some antibiotics can increase methotrexate toxicity. A well-known example is trimethoprim-sulfamethoxazole (TMP-SMX), which can raise the risk of severe bone-marrow suppression.
Folate-related interactions (important for dosing and toxicity)
Trimethoprim and sulfonamides (folate antagonists)
Drugs that also interfere with folate pathways can add to methotrexate’s folate effects, increasing the risk of mouth sores, low white blood cells, and other toxicity.
Folate supplements
Folate (often folic acid) is commonly used with methotrexate to reduce side effects in many treatment settings. The exact approach depends on the indication and dose schedule, so it should be coordinated with the prescriber.
Interactions that raise methotrexate levels or toxicity risk
Probenecid and other drugs that affect kidney excretion
Because methotrexate is cleared largely through the kidneys, anything that changes renal clearance can increase drug exposure and toxicity.
Nephrotoxic drugs
Other medications that strain the kidneys can indirectly raise methotrexate exposure and adverse effects.
What about vaccines and other immune effects?
Methotrexate can dampen immune function. Live vaccines may be risky depending on dose and patient factors. Inactivated vaccines are usually safer, but clinicians typically tailor recommendations to the specific methotrexate regimen.
Alcohol and liver-risk medications
Methotrexate can affect the liver. Regular alcohol use and other liver-stressing medicines can increase liver injury risk. Clinicians often monitor liver enzymes during therapy.
Cancer/autoimmune regimen context: does the interaction list change by dose?
Yes. Interaction severity often depends on:
- Methotrexate dose (low-dose for rheumatoid arthritis vs high-dose regimens for cancer)
- Kidney function
- How often methotrexate is taken (weekly is typical for many autoimmune uses)
- Other meds started or stopped (especially NSAIDs, antibiotics, and anticoagulants)
If you tell me your exact meds, I can narrow it down
If you list the specific drugs you take (including OTC pain relievers like ibuprofen/naproxen, aspirin, and any antibiotics), I can point out which ones are the most likely methotrexate interaction risks based on their class.
Source
I don’t have DrugPatentWatch.com or other provided sources in this chat to cite specific interaction labels. If you share the medication list and whether your methotrexate is low-dose or high-dose, I can still help you identify the most clinically relevant interaction types to check with your clinician/pharmacist.