What the FDA labels say about taking them together
Divalproex and ethosuximide
Divalproex's FDA label of March 31, 2026 names ethosuximide in its drug interactions section, and ethosuximide's label names divalproex too. The ethosuximide label: “Drug Interactions: Since Zarontin (ethosuximide) may interact with concurrently administered antiepileptic drugs, periodic serum level determinations of these drugs may be necessary.”
Check it at the source: the divalproex FDA label on DailyMed (effective March 31, 2026, AbbVie Inc.); the ethosuximide FDA label on DailyMed (effective June 11, 2026, Chartwell Governmental & Specialty RX, LLC.).
What does the divalproex label say about ethosuximide?
Divalproex label, drug interactionsMonitoring of valproate concentrations is recommended ( 7.1 ) Co-administration of valproate can affect the pharmacokinetics of other drugs (e.g., diazepam, ethosuximide, lamotrigine, phenytoin) by inhibiting their metabolism or protein binding displacement ( 7.2 ) Patients stabilized on rufinamide should begin valproate therapy at a low dose, and titrate to clinically effective dose ( 7.2 ) Dosage adjustment of amitriptyline/nortriptyline, propofol, warfarin, and zidovudine may be necessary if used concomitantly with Depakote ( 7.2 ) Topiramate:
Source: FDA drug label (Depakote), AbbVie Inc., effective March 31, 2026 (SPL set 08a65cf4-7749-4ceb-6895-8f4805e2b01f), via openFDA; the full label on DailyMed
What does the ethosuximide label say about divalproex?
Zarontin label (Parke-Davis Div of Pfizer Inc, May 25, 2026), drug interactionsDrug Interactions: Since Zarontin (ethosuximide) may interact with concurrently administered antiepileptic drugs, periodic serum level determinations of these drugs may be necessary (e.g., ethosuximide may elevate phenytoin serum levels and valproic acid has been reported to both increase and decrease ethosuximide levels).
Source: FDA drug label (Zarontin, NDA012380), Parke-Davis Div of Pfizer Inc, effective May 25, 2026 (SPL set 0e008f33-70a1-4bc6-b3a0-d45214418ab6), via openFDA
Source: FDA drug label (Ethosuximide), Chartwell Governmental & Specialty RX, LLC., effective June 11, 2026 (SPL set a825265d-ace9-4463-a16d-f6d5e1e31188), 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
| Divalproex | Ethosuximide | |
|---|---|---|
| Labeled for | Bipolar disorder, Migraine, Seizures and epilepsy | Seizures and epilepsy |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.194 per tablet 500 mg tablet | $0.243 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