What the FDA labels say about taking them together
Primidone and tiagabine
Tiagabine's FDA label of September 30, 2021 names primidone in its drug interactions section; primidone's label does not name tiagabine itself but warns about its class (Anti-seizure medicines). The tiagabine label: “The tiagabine HCl dosing recommendations in current labeling for treatment of epilepsy were based on use in patients with partial seizures 12 years of age and older, most of whom were taking enzyme-inducing …”
Check it at the source: the primidone FDA label on DailyMed (effective September 10, 2026, Bausch Health US, LLC); the tiagabine FDA label on DailyMed (effective September 30, 2021, Teva Pharmaceuticals USA, Inc.).
What does the primidone label say about tiagabine?
Primidone's label does not name tiagabine itself; it warns about its class (Anti-seizure medicines):
Primidone label, warningsSuicidal Behavior and Ideation Antiepileptic drugs (AEDs), including MYSOLINE, increase the risk of suicidal thoughts or behavior in patients taking these drugs for any indication.
Primidone label, warningsPatients treated with any AED for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior.
Source: FDA drug label (Mysoline), NDA009170 (Valeant), as published by Bausch Health US, LLC, effective September 10, 2026 (SPL set af593171-dabb-4ea3-b44c-89ed457b2c46), via openFDA; the full label on DailyMed
What does the tiagabine label say about primidone?
Tiagabine label, drug interactionsCarbamazepine, phenytoin, primidone, and phenobarbital are generally classified as enzyme inducers; valproate and gabapentin are not.
Tiagabine label, warningsThe tiagabine HCl dosing recommendations in current labeling for treatment of epilepsy were based on use in patients with partial seizures 12 years of age and older, most of whom were taking enzyme-inducing antiepileptic drugs (AEDs; e.g., carbamazepine, phenytoin, primidone and phenobarbital) which lower plasma levels of tiagabine HCl by inducing its metabolism.
Source: FDA drug label (Tiagabine Hydrochloride), NDA020646 (Cephalon), as published by Teva Pharmaceuticals USA, Inc., effective September 30, 2021 (SPL set 953ef3cc-e3cb-480f-b9ea-256520fd62b8), 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
| Primidone | Tiagabine | |
|---|---|---|
| Labeled for | Seizures and epilepsy | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.0914 per tablet 50 mg tablet | $2.62 per tablet 2 mg tablet |
| Shortage now | No current entry | A presentation being discontinued |
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