What the FDA labels say about taking them together
Metformin and topiramate
Metformin's FDA label of September 3, 2026 names topiramate in its boxed warning section; the topiramate labels PlainMeds reads (4) do not name metformin. The metformin label: “Carbonic anhydrase inhibitors frequently cause a decrease in serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis. …”
Check it at the source: the metformin FDA label on DailyMed (effective September 3, 2026, Granules India Ltd); the topiramate FDA label on DailyMed (effective June 1, 2026, Sun Pharmaceutical Industries, Inc.).
What does the metformin label say about topiramate?
Metformin label, boxed warningRisk factors for metformin-associated lactic acidosis include renal impairment, concomitant use of certain drugs (e.g., carbonic anhydrase inhibitors such as topiramate), age 65 years old or greater, having a radiological study with contrast, surgery and other procedures, hypoxic states (e.g., acute congestive heart failure), excessive alcohol intake, hepatic impairment, and mitochondrial diseases [see Warnings and Precautions (5.1)].
Metformin label, drug interactionsCarbonic Anhydrase Inhibitors Clinical Impact: Carbonic anhydrase inhibitors frequently cause a decrease in serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis. Concomitant use of these drugs with metformin hydrochloride extended-release tablets may increase the risk for lactic acidosis. Intervention: Consider more frequent monitoring of these patients. Examples: Topiramate, zonisamide, acetazolamide or dichlorphenamide.
Source: FDA drug label (Riomet, NDA021591), Sun Pharmaceutical Industries, Inc., effective December 6, 2018 (SPL set 05d4df4b-dfe8-4828-b423-a3d4f2c4114a), via openFDA
Source: FDA drug label (METFORMIN HYDROCHLORIDE), Granules India Ltd, effective September 3, 2026 (SPL set 73197cb5-3e23-4ac0-b189-f9bc848bce66), via openFDA; the full label on DailyMed
What does the topiramate label say about metformin?
Topiramate's label (effective June 1, 2026) and its 3 other brand-application labels do not name metformin in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Topiramate), Sun Pharmaceutical Industries, Inc., effective June 1, 2026 (SPL set 3c909a53-ae66-4b28-a741-b60bb25a69cf), 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
| Metformin | Topiramate | |
|---|---|---|
| Labeled for | Type 2 diabetes | Seizures and epilepsy, Migraine |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.0145 per tablet 500 mg tablet | $0.0567 per tablet 100 mg tablet |
| 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