Drug interactions
Mefenamic acid + Warfarin
Severity: Major
Mefenamic acid and Warfarin: major interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Mefenamic acid inhibits platelet function and can cause gastrointestinal ulceration, which raises bleeding risk in anticoagulated patients. It may also increase warfarin effect by displacing it from protein binding and inhibiting CYP2C9. Serious gastrointestinal bleeding can result.
What this interaction means in plain words
Mefenamic acid and Warfarin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Mefenamic acid belongs to Musculoskeletal; Warfarin belongs to Cardiovascular.
Why it happens
Additive impairment of hemostasis through platelet inhibition and GI mucosal injury, plus possible CYP2C9 inhibition and protein binding displacement raising warfarin effect.
What to do
Avoid NSAIDs in warfarin-treated patients and use paracetamol instead where suitable. If unavoidable, monitor INR closely and consider gastroprotection.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Mefenamic acid
- Ketorolac intranasal + Mefenamic acid Contraindicated
- Ketorolac + Mefenamic acid Contraindicated
- Aceclofenac + Mefenamic acid Major
- Acemetacin + Mefenamic acid Major
- Acetylsalicylic acid + Mefenamic acid Major
- Alteplase + Mefenamic acid Major
Other interactions of Warfarin
- Defibrotide + Warfarin Contraindicated
- Ketorolac + Warfarin Contraindicated
- Abciximab + Warfarin Major
- Acetylsalicylic acid + Warfarin Major
- Adagrasib + Warfarin Major
- Amiodarone + Warfarin Major
Frequently asked questions
Can I take Mefenamic acid with Warfarin?
MediHelp rates the interaction as major. Mefenamic acid and Warfarin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Mefenamic acid inhibits platelet function and can cause gastrointestinal ulceration, which raises bleeding risk in anticoagulated patients. It may also increase warfarin effect by displacing it from protein binding and inhibiting CYP2C9. Serious gastrointestinal bleeding can result.
How serious is the interaction between Mefenamic acid and Warfarin?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid NSAIDs in warfarin-treated patients and use paracetamol instead where suitable. If unavoidable, monitor INR closely and consider gastroprotection.
What other medicines interact with Mefenamic acid?
MediHelp also lists interactions of Mefenamic acid with, for example, Ketorolac intranasal, Ketorolac, Aceclofenac. The full list is on the Mefenamic acid page.
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