What the FDA labels say about taking them together
Topiramate and zonisamide
Topiramate's FDA label of June 1, 2026 names zonisamide in its drug interactions section, and zonisamide's label names topiramate too. The zonisamide label: “… other medications that can cause hyperammonemia, including valproic acid or topiramate.”
Check it at the source: the topiramate FDA label on DailyMed (effective June 1, 2026, Sun Pharmaceutical Industries, Inc.); the zonisamide FDA label on DailyMed (effective June 4, 2026, Sun Pharmaceutical Industries, Inc.).
What does the topiramate label say about zonisamide?
Topiramate label, drug interactionsConcomitant use of topiramate, a carbonic anhydrase inhibitor, with any other carbonic anhydrase inhibitor (e.g., zonisamide or acetazolamide) may increase the severity of metabolic acidosis and may also increase the risk of kidney stone formation.
Source: FDA drug label (Eprontia, NDA214679), Azurity Pharmaceuticals, Inc., effective November 13, 2025 (SPL set e2a4df59-fead-4a01-9021-9eda02c48010), via openFDA
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
What does the zonisamide label say about topiramate?
Zonisamide label, warningsThe risks of hyperammonemia and various manifestations of encephalopathy may be increased in patients treated with zonisamide and concomitantly taking other medications that can cause hyperammonemia, including valproic acid or topiramate (see PRECAUTIONS ).
Zonegran label (Advanz Pharma (US) Corp., September 12, 2025), drug interactionsOther Carbonic Anhydrase Inhibitors: Concomitant use of ZONEGRAN, a carbonic anhydrase inhibitor, with any other carbonic anhydrase inhibitor (e.g., topiramate, acetazolamide or dichlorphenamide), may increase the severity of metabolic acidosis and may also increase the risk of kidney stone formation or the risk of hyperammonemia.
Source: FDA drug label (Zonisade, NDA214273), Azurity Pharmaceuticals, Inc., effective September 8, 2025 (SPL set ac16fa15-32e9-4f92-8bc6-d8d41ae002c6), via openFDA
Source: FDA drug label (Zonegran, NDA020789), Advanz Pharma (US) Corp., effective September 12, 2025 (SPL set d12de43e-3ac3-4335-bc85-70d7366a91eb), via openFDA
Source: FDA drug label (Zonisamide), Sun Pharmaceutical Industries, Inc., effective June 4, 2026 (SPL set 3164d438-90bf-420a-9a56-5498b987f91c), 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
| Topiramate | Zonisamide | |
|---|---|---|
| Labeled for | Seizures and epilepsy, Migraine | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.0567 per tablet 100 mg tablet | $0.106 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