What the FDA labels say about taking them together
Lamotrigine and valproic acid
Lamotrigine's FDA label of October 10, 2025 names valproic acid in its boxed warning section, and valproic acid's label names lamotrigine too. The valproic acid label: “… exposure to the other antiepileptic drug monotherapy treatments evaluated: lamotrigine (108 [95% C.I. 105-110]), carbamazepine (105 [95% C.I. 102-108]), and phenytoin (108 [95% C.I. 104-112]).”
Check it at the source: the lamotrigine FDA label on DailyMed (effective October 10, 2025); the valproic acid FDA label on DailyMed (effective January 24, 2025, PAI Holdings, LLC dba PAI Pharma).
What does the lamotrigine label say about valproic acid?
Lamotrigine label, boxed warningIn addition to age, factors that may increase the risk of occurrence or the severity of rash caused by LAMICTAL include (1) coadministration of LAMICTAL with valproate (includes valproic acid and divalproex sodium), (2) exceeding the recommended initial dose of LAMICTAL, (3) exceeding the recommended dose escalation for LAMICTAL, or (4) the presence of the HLA-B*1502 allele.
Source: FDA drug label (Lamictal Xr, NDA022115), GlaxoSmithKline LLC, effective October 10, 2025 (SPL set 3e2c9a35-6a39-41d7-ad84-3c0bb8894b09), via openFDA
Source: FDA drug label (Subvenite, NDA218879), OWP Pharmaceuticals, Inc., effective June 4, 2026 (SPL set 022b0913-f683-4af8-a862-f81b315909b2), via openFDA
Source: FDA drug label (LAMICTAL), GlaxoSmithKline LLC, effective October 10, 2025 (SPL set d7e3572d-56fe-4727-2bb4-013ccca22678), via openFDA; the full label on DailyMed
What does the valproic acid label say about lamotrigine?
Valproic acid 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 Valproic acid ( 7.2 ) Topiramate: Hyperammonemia and encephalopathy
Valproic acid label, warnings and precautionsThe largest of these studies 1 is a prospective cohort study conducted in the United States and United Kingdom that found that children with prenatal exposure to valproate (n=62) had lower IQ scores at age 6 (97 [95% C.I. 94-101]) than children with prenatal exposure to the other antiepileptic drug monotherapy treatments evaluated: lamotrigine (108 [95% C.I. 105-110]), carbamazepine (105 [95% C.I. 102-108]), and phenytoin (108 [95% C.I. 104-112]).
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
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
| Lamotrigine | Valproic acid | |
|---|---|---|
| Labeled for | Seizures and epilepsy, Bipolar disorder | Seizures and epilepsy, Migraine |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.0268 per tablet 25 mg tablet | $0.243 per capsule 250 mg capsule |
| Shortage now | A presentation being discontinued | Listed; available |
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