Major
Acetylsalicylic acid × Methotrexate
Antiplatelet agents (low dose) / NSAIDs (analgesic dose)×Antimetabolites, folic acid analogues
Mechanism
Aspirin suppresses tubular secretion of methotrexate and displaces it from albumin binding. Methotrexate plasma levels rise – particularly dangerous at oncologic doses.
Symptoms
Mouth ulcers (mucositis), nausea, diarrhoea, hair loss. Blood counts fall: leukocytes, platelets, erythrocytes. Severe cases include fatal pancytopenia, nephrotoxicity, and hepatotoxicity.
Management
At oncologic methotrexate doses, the combination is not prescribed. At low rheumatologic doses (5–25 mg/week), cardioprotective aspirin (75–100 mg/day) is acceptable when renal function is preserved, with full blood count and creatinine every 1–3 months.
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.