What the FDA labels say about taking them together
Lithium and mefenamic acid
Mefenamic acid's FDA label of April 20, 2026 names lithium in its drug interactions section; lithium's label does not name mefenamic acid itself but warns about its class (NSAIDs (nonsteroidal anti-inflammatory drugs)). The mefenamic acid label: “NSAIDs have produced elevations in plasma lithium levels and reductions in renal lithium clearance. This effect has been attributed to NSAID inhibition of renal prostaglandin synthesis.”
Check it at the source: the lithium FDA label on DailyMed (effective December 23, 2025, Glenmark Pharmaceuticals Inc., USA); the mefenamic acid FDA label on DailyMed (effective April 20, 2026, Lupin Pharmaceuticals, Inc.).
What does the lithium label say about mefenamic acid?
Lithium's label does not name mefenamic acid itself; it warns about its class (NSAIDs (nonsteroidal anti-inflammatory drugs)):
Lithium label, drug interactionsDiuretics, NSAID, renin-angiotensin system antagonists, or metronidazole may increase lithium serum concentrations.
Lithium label, drug interactionsReduce lithium dosage based on serum lithium concentration and clinical response [see Dosage and Administration ( 2.3 ), Warning and Precautions ( 5.3 )]. Non-Steroidal Anti-inflammatory Drugs (NSAID)
Source: FDA drug label (Lithium Carbonate), Glenmark Pharmaceuticals Inc., USA, effective December 23, 2025 (SPL set 63b3790f-a9b5-47f4-bae1-ddf8b43c13c1), via openFDA; the full label on DailyMed
What does the mefenamic acid label say about lithium?
Mefenamic acid label, drug interactionsClinical Impact: NSAIDs have produced elevations in plasma lithium levels and reductions in renal lithium clearance. This effect has been attributed to NSAID inhibition of renal prostaglandin synthesis [See Clinical Pharmacology ( 12.3 )]. Intervention: During concomitant use of mefenamic acid and lithium, monitor patients for signs of lithium toxicity.
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
| Lithium | Mefenamic acid | |
|---|---|---|
| Labeled for | Bipolar disorder | Pain |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.104 per capsule 300 mg capsule | $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