What the FDA labels say about taking them together
Carbamazepine and letermovir
Letermovir's FDA label of January 14, 2026 names carbamazepine in its drug interactions section; the carbamazepine labels PlainMeds reads (3) do not name letermovir. The letermovir label: “Co-administration of PREVYMIS and carbamazepine is not recommended due to potential for loss of efficacy of PREVYMIS.”
Check it at the source: the carbamazepine FDA label on DailyMed (effective August 20, 2026, Novartis Pharmaceuticals Corporation); the letermovir FDA label on DailyMed (effective January 14, 2026, Merck Sharp & Dohme LLC).
What does the carbamazepine label say about letermovir?
Carbamazepine's label (effective August 20, 2026) and its 2 other brand-application labels do not name letermovir in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Tegretol), Novartis Pharmaceuticals Corporation, effective August 20, 2026 (SPL set 8d409411-aa9f-4f3a-a52c-fbcb0c3ec053), via openFDA; the full label on DailyMed
What does the letermovir label say about carbamazepine?
Letermovir label, drug interactionsConcomitant Drug Class and/or Clearance Pathway/Drug Name: carbamazepine; Effect on Concentration ↓ =decrease, ↑ =increase: ↓ letermovir; Clinical Comments: Co-administration of PREVYMIS and carbamazepine is not recommended due to potential for loss of efficacy of PREVYMIS.
Source: FDA drug label (PREVYMIS), Merck Sharp & Dohme LLC, effective January 14, 2026 (SPL set 1b49df80-be4f-47e0-a0b7-123f3e69395b), 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
| Carbamazepine | Letermovir | |
|---|---|---|
| Labeled for | Bipolar disorder, Seizures and epilepsy | n/a |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.119 per tablet 200 mg tablet | n/a |
| Shortage now | A presentation being discontinued | 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