What the FDA labels say about taking them together
Lamotrigine and ritonavir
Lamotrigine's FDA label of October 10, 2025 names ritonavir in its drug interactions section, and ritonavir's label names lamotrigine too. The lamotrigine label: “Decreased lamotrigine concentration approximately 50%.”
Check it at the source: the lamotrigine FDA label on DailyMed (effective October 10, 2025); the ritonavir FDA label on DailyMed (effective July 23, 2026, AbbVie Inc.).
What does the lamotrigine label say about ritonavir?
Lamotrigine label, drug interactionsConcomitant Drug: Lopinavir/ritonavir; Effect on Concentration of Lamotrigine or Concomitant Drug: ↓ lamotrigine; Clinical Comment: Decreased lamotrigine concentration approximately 50%.
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 ritonavir label say about lamotrigine?
Ritonavir label, drug interactionsConcomitant Drug Class/Drug Name: Anticonvulsants: divalproex, lamotrigine, phenytoin; Effect on Concentration of Ritonavir or Concomitant Drug: ↓ anticonvulsants; Clinical Comment: A dose increase may be needed for these drugs when co-administered with ritonavir and therapeutic concentration monitoring is recommended for these anticonvulsants, if available.
Source: FDA drug label (Norvir), AbbVie Inc., effective July 23, 2026 (SPL set 2849298e-de6e-47bb-8194-56e075b33fc3), 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 | Ritonavir | |
|---|---|---|
| Labeled for | Seizures and epilepsy, Bipolar disorder | HIV |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.0268 per tablet 25 mg tablet | $0.607 per tablet 100 mg tablet |
| Shortage now | A presentation being discontinued | 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