Major
Methotrexate × naproxen
Antimetabolites, folic acid analogues×NSAID, propionic acid derivative
Mechanism
Naproxen reduces methotrexate renal clearance by 30–40%. Naproxen has a long half-life (12–17 h), so the effect lasts longer than with ibuprofen. With high-dose oncological methotrexate the combination is contraindicated.
Symptoms
Mucositis, leukopenia, thrombocytopenia, rising creatinine within 1–2 weeks.
Management
With low-dose methotrexate, lab monitoring every 2 weeks for the first 2 months. With high-dose therapy, stop naproxen 3 days before infusion and resume no sooner than 3 days after.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.