What the FDA labels say about taking them together
Diflunisal and mefenamic acid
Mefenamic acid's FDA label of April 20, 2026 names diflunisal in its drug interactions section; diflunisal's label does not name mefenamic acid itself but warns about its class (NSAIDs (nonsteroidal anti-inflammatory drugs)). The mefenamic acid label: “Concomitant use of mefenamic acid with other NSAIDs or salicylates increases the risk of GI toxicity, with little or no increase in efficacy.”
Check it at the source: the diflunisal FDA label on DailyMed (effective August 4, 2026, Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc.); the mefenamic acid FDA label on DailyMed (effective April 20, 2026, Lupin Pharmaceuticals, Inc.).
What does the diflunisal label say about mefenamic acid?
Diflunisal's label does not name mefenamic acid itself; it warns about its class (NSAIDs (nonsteroidal anti-inflammatory drugs)):
Diflunisal label, boxed warningGastrointestinal Risk NSAIDs cause an increased risk of serious gastrointestinal adverse events including bleeding, ulceration, and perforation of the stomach or intestines, which can be fatal.
Diflunisal label, warningsGastrointestinal Effects – Risk of Ulceration, Bleeding and Perforation NSAIDs, including diflunisal tablets, can cause serious gastrointestinal (GI) adverse events including inflammation, bleeding, ulceration, and perforation of the stomach, small intestine, or large intestine, which can be fatal.
Source: FDA drug label (diflunisal), Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc., effective August 4, 2026 (SPL set 666f89b4-fd81-420a-a390-eb1cd4014f61), via openFDA; the full label on DailyMed
What does the mefenamic acid label say about diflunisal?
Mefenamic acid label, drug interactionsNSAIDs and Salicylates Clinical Impact: Concomitant use of mefenamic acid with other NSAIDs or salicylates (…) increases the risk of GI toxicity, with little or no increase in efficacy. Intervention: The concomitant use of mefenamic acid with other NSAIDs or salicylates is not recommended.
Source: FDA drug label (Mefenamic Acid), Lupin Pharmaceuticals, Inc., effective April 20, 2026 (SPL set d15733a9-d5fd-4d5f-86ce-e7ed8c706c7f), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Diflunisal | Mefenamic acid | |
|---|---|---|
| Labeled for | Pain, Osteoarthritis, Rheumatoid arthritis | Pain |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $1.06 per tablet 500 mg tablet | $0.948 per capsule 250 mg capsule |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once