What the FDA labels say about taking them together
Magnesium hydroxide and mefenamic acid
Mefenamic acid's FDA label of April 20, 2026 names magnesium hydroxide in its drug interactions section; the magnesium hydroxide label PlainMeds reads does not name mefenamic acid. The mefenamic acid label: “Concomitant ingestion of antacids containing magnesium hydroxide has been shown to significantly increase the rate and extent of mefenamic acid absorption”
Check it at the source: the magnesium hydroxide FDA label on DailyMed (effective August 21, 2026); the mefenamic acid FDA label on DailyMed (effective April 20, 2026, Lupin Pharmaceuticals, Inc.).
What does the magnesium hydroxide label say about mefenamic acid?
Magnesium hydroxide's label (effective August 21, 2026) does not name mefenamic acid in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (MiraFAST soft chews), Bayer HealthCare LLC., effective August 21, 2026 (SPL set 2cee67dd-b71f-32b8-e063-6394a90ae864), via openFDA; the full label on DailyMed
What does the mefenamic acid label say about magnesium hydroxide?
Mefenamic acid label, drug interactionsAntacid Clinical Impact: Concomitant ingestion of antacids containing magnesium hydroxide has been shown to significantly increase the rate and extent of mefenamic acid absorption [See Clinical Pharmacology ()] Intervention: Concomitant use of mefenamic acid and antacids is not generally recommended because of possible increased adverse events.
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
| Magnesium hydroxide | Mefenamic acid | |
|---|---|---|
| Labeled for | Constipation, Acid reflux and ulcers | Pain |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.0095 per mL Milk of magnesia suspension | $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