Which medications are most impacted by methotrexate?

What other drugs does methotrexate interact with most strongly?

Methotrexate levels in the body rise sharply when taken with certain painkillers and antibiotics. NSAIDs such as ibuprofen, naproxen, and aspirin displace methotrexate from binding sites and slow its elimination through the kidneys. Antibiotics including trimethoprim-sulfamethoxazole, penicillins, and tetracyclines inhibit methotrexate's renal excretion, raising toxicity risk.

How do these interactions affect patients taking methotrexate?

Elevated methotrexate leads to bone-marrow suppression, liver damage, and gastrointestinal toxicity. Patients who need these companion drugs must have frequent blood tests or receive folinic acid rescue. Many physicians substitute acetaminophen for NSAIDs or avoid trimethoprim altogether unless monitoring is tight.

Why are companies challenging this patent?

No.