Drug interactions
Mefenamic acid + Phenindione
Severity: Major
Mefenamic acid and Phenindione: 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
Phenindione is an oral anticoagulant and mefenamic acid impairs platelet function and can cause gastrointestinal ulceration. Together they substantially raise the risk of serious bleeding, and mefenamic acid may also displace anticoagulant from protein binding.
What this interaction means in plain words
Mefenamic acid and Phenindione 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.
Why it happens
Additive hemostatic impairment from vitamin K antagonism and NSAID platelet inhibition with mucosal injury, possibly with protein-binding displacement.
What to do
Avoid the combination and use paracetamol for analgesia; if unavoidable, monitor INR and signs of bleeding 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
Frequently asked questions
Can I take Mefenamic acid with Phenindione?
MediHelp rates the interaction as major. Mefenamic acid and Phenindione 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. Phenindione is an oral anticoagulant and mefenamic acid impairs platelet function and can cause gastrointestinal ulceration. Together they substantially raise the risk of serious bleeding, and mefenamic acid may also displace anticoagulant from protein binding.
How serious is the interaction between Mefenamic acid and Phenindione?
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 the combination and use paracetamol for analgesia; if unavoidable, monitor INR and signs of bleeding 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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