Diflunisal and Methotrexate Interaction

Understanding the Diflunisal and Methotrexate Interaction

FDA-approved prescribing information for these two drugs flags their combination as a moderate-severity interaction. Diflunisal belongs to the Nonsteroidal Anti-Inflammatory Drug (NSAID) class and Methotrexate belongs to the Disease-Modifying Antirheumatic Drug (DMARD) class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Diflunisal can prevent your kidneys from clearing methotrexate out of your system, which can lead to toxic levels of the drug in your blood. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.

Context around a specific patient determines real-world impact. Diflunisal has 17 total documented interactions on file in this dataset, and Methotrexate has 38. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Be very careful when using these drugs together and make sure your doctor monitors your health and blood work closely. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.

An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Diflunisal or Methotrexate based on a web page, speak with your prescriber or pharmacist before making any change.