What the FDA labels say about taking them together
Valproic acid and zonisamide
Zonisamide's FDA label of June 4, 2026 names valproic acid in its warnings section; valproic acid's label does not name zonisamide itself but warns about its class (Anti-seizure medicines). The zonisamide label: “… concomitantly taking other medications that can cause hyperammonemia, including valproic acid or topiramate.”
Check it at the source: the valproic acid FDA label on DailyMed (effective January 24, 2025, PAI Holdings, LLC dba PAI Pharma); the zonisamide FDA label on DailyMed (effective June 4, 2026, Sun Pharmaceutical Industries, Inc.).
What does the valproic acid label say about zonisamide?
Valproic acid's label does not name zonisamide itself; it warns about its class (Anti-seizure medicines):
Valproic acid label, warnings and precautionsAntiepileptic drugs, including valproic acid, increase the risk of suicidal thoughts or behavior ( 5.7 ) Bleeding and other hematopoietic disorders; monitor platelet counts and coagulation tests ( 5.8 ) Hyperammonemia and hyperammonemic encephalopathy; measure ammonia level if unexplained lethargy and vomiting or changes in mental status, and also with concomitant topiramate use; consider discontinuation of valproate therapy ( 5.6 , 5.9 , 5.10 ) Hypothermia;
Valproic acid label, warnings and precautionsFollowing in utero Exposure Valproate can cause decreased IQ scores following in utero exposure. Published epidemiological studies have indicated that children exposed to valproate in utero have lower cognitive test scores than children exposed in utero to either another antiepileptic drug or to no antiepileptic drugs.
Source: FDA drug label (VALPROIC ACID), PAI Holdings, LLC dba PAI Pharma, effective January 24, 2025 (SPL set 7d5cb52e-37dd-4dfa-a6f4-09f9548846c6), via openFDA; the full label on DailyMed
What does the zonisamide label say about valproic acid?
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 ).
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 (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
| Valproic acid | Zonisamide | |
|---|---|---|
| Labeled for | Seizures and epilepsy, Migraine | Seizures and epilepsy |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.243 per capsule 250 mg capsule | $0.106 per capsule 100 mg capsule |
| Shortage now | Listed; available | 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