What the FDA labels say about taking them together
Furosemide and mefenamic acid
Mefenamic acid's FDA label of April 20, 2026 names furosemide in its drug interactions section; furosemide's label does not name mefenamic acid itself but warns about its class (NSAIDs (nonsteroidal anti-inflammatory drugs)). The mefenamic acid label: “Clinical studies, as well as post-marketing observations, showed that NSAIDs reduced the natriuretic effect of loop diuretics (e.g., furosemide) and thiazide diuretics in some patients. …”
Check it at the source: the furosemide FDA label on DailyMed (effective September 30, 2025, Validus Pharmaceuticals LLC); the mefenamic acid FDA label on DailyMed (effective April 20, 2026, Lupin Pharmaceuticals, Inc.).
What does the furosemide label say about mefenamic acid?
Furosemide's label does not name mefenamic acid itself; it warns about its class (NSAIDs (nonsteroidal anti-inflammatory drugs)):
Furosemide label, drug interactionsThere are case reports of patients who developed increased BUN, serum creatinine and serum potassium levels, and weight gain when furosemide was used in conjunction with NSAIDs.
Source: FDA drug label (Lasix), Validus Pharmaceuticals LLC, effective September 30, 2025 (SPL set 2c9b4d8f-0770-482d-a9e6-9c616a440b1a), via openFDA; the full label on DailyMed
What does the mefenamic acid label say about furosemide?
Mefenamic acid label, drug interactionsDiuretics Clinical Impact: Clinical studies, as well as post-marketing observations, showed that NSAIDs reduced the natriuretic effect of loop diuretics (e.g., furosemide) and thiazide diuretics in some patients. This effect has been attributed to the NSAID inhibition of renal prostaglandin synthesis. Intervention: During concomitant use of mefenamic acid with diuretics, observe patients for signs of worsening renal function, in addition to assuring diuretic efficacy including antihypertensive effects [see Warnings and Precautions ()].
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
| Furosemide | Mefenamic acid | |
|---|---|---|
| Labeled for | Heart failure, High blood pressure, Edema (fluid retention) | Pain |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.490 per mL 20 mg/2 mL vial | $0.948 per capsule 250 mg capsule |
| Shortage now | In shortage | 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