What the FDA labels say about taking them together
Letermovir and voriconazole
Letermovir's FDA label of January 14, 2026 names voriconazole in its drug interactions section, and voriconazole's label names letermovir too. The letermovir label: “If concomitant administration of voriconazole is necessary, closely monitor for reduced effectiveness of voriconazole.”
Check it at the source: the letermovir FDA label on DailyMed (effective January 14, 2026, Merck Sharp & Dohme LLC); the voriconazole FDA label on DailyMed (effective February 26, 2026, Roerig).
What does the letermovir label say about voriconazole?
Letermovir label, drug interactionsConcomitant Drug Class and/or Clearance Pathway/Drug Name: voriconazole These interactions have been studied [see ].; Effect on Concentration ↓ =decrease, ↑ =increase: ↓ voriconazole; Clinical Comments: If concomitant administration of voriconazole is necessary, closely monitor for reduced effectiveness of voriconazole.
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
What does the voriconazole label say about letermovir?
Voriconazole label, drug interactionsLetermovir (CYP2C9/2C19 Induction) Reduced If concomitant administration of voriconazole with letermovir cannot be avoided, monitor for reduced effectiveness of voriconazole.
Voriconazole label (Xellia Pharmaceuticals USA LLC, January 11, 2023), drug interactionsDrug/Drug Class (Mechanism of Interaction by the Drug): Letermovir (CYP2C9/2C19 Induction); Voriconazole Plasma Exposure (C max and AUC τ after 200 mg every 12 hours): Reduced; Recommendations for Voriconazole Dosage Adjustment/Comments: If concomitant administration of voriconazole with letermovir cannot be avoided, monitor for reduced effectiveness of voriconazole.
Source: FDA drug label (Voriconazole, NDA208562), Xellia Pharmaceuticals USA LLC, effective January 11, 2023 (SPL set 9ec6eda2-2f15-423b-9ec6-819379a426e1), via openFDA
Source: FDA drug label (VFEND), NDA021630 (Pf Prism Cv), as published by Roerig, effective February 26, 2026 (SPL set ce3ef5cf-3087-4d92-9d94-9eb8287228db), 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
| Letermovir | Voriconazole | |
|---|---|---|
| Labeled for | n/a | Fungal infections |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $1.88 per tablet 200 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