What the FDA labels say about taking them together
Magnesium hydroxide and phenytoin
Phenytoin's FDA label of October 15, 2024 names magnesium hydroxide in its drug interactions section; the magnesium hydroxide label PlainMeds reads does not name phenytoin.
Check it at the source: the magnesium hydroxide FDA label on DailyMed (effective August 21, 2026); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the magnesium hydroxide label say about phenytoin?
Magnesium hydroxide's label (effective August 21, 2026) does not name phenytoin 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 phenytoin label say about magnesium hydroxide?
Phenytoin label, drug interactionsInteracting Agent: Antacids Antacids may affect absorption of phenytoin.; Examples: Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day
Source: FDA drug label (Phenytek), Mylan Pharmaceuticals Inc., effective October 15, 2024 (SPL set 0f94c791-8b07-4b41-927e-c9f28bec5f60), 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 | Phenytoin | |
|---|---|---|
| Labeled for | Constipation, Acid reflux and ulcers | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.0095 per mL Milk of magnesia suspension | $0.145 per capsule 100 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