Drug interactions
Diflunisal + Mefenamic acid
Severity: Major
Diflunisal and Mefenamic acid: major interaction.
Last updated Sources: US FDA label
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
Combining two systemic NSAIDs adds no meaningful therapeutic benefit but increases the risk of gastrointestinal ulceration and bleeding, renal impairment and fluid retention. Platelet inhibition from both agents is additive.
What this interaction means in plain words
Diflunisal and Mefenamic acid 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.
Diflunisal belongs to Musculoskeletal; Mefenamic acid belongs to Musculoskeletal.
Why it happens
Additive inhibition of cyclooxygenase-1 and -2 causing duplicated antiplatelet effects, loss of gastric mucosal protection and reduced renal prostaglandin synthesis.
What to do
Avoid concurrent use of two NSAIDs and use a single agent at the lowest effective dose. If an NSAID switch is made, stop the first drug before starting the second.
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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References
Other interactions of Diflunisal
- Diflunisal + Ketorolac Contraindicated
- Diflunisal + Ketorolac intranasal Contraindicated
- Acemetacin + Diflunisal Major
- Acetazolamide + Diflunisal Major
- Alteplase + Diflunisal Major
- Amiloride + Diflunisal Major
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 Diflunisal with Mefenamic acid?
MediHelp rates the interaction as major. Diflunisal and Mefenamic acid 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. Combining two systemic NSAIDs adds no meaningful therapeutic benefit but increases the risk of gastrointestinal ulceration and bleeding, renal impairment and fluid retention. Platelet inhibition from both agents is additive.
How serious is the interaction between Diflunisal and Mefenamic acid?
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 concurrent use of two NSAIDs and use a single agent at the lowest effective dose. If an NSAID switch is made, stop the first drug before starting the second.
What other medicines interact with Diflunisal?
MediHelp also lists interactions of Diflunisal with, for example, Ketorolac, Ketorolac intranasal, Acemetacin. The full list is on the Diflunisal page.
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