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Does Letermovir Interact with Voriconazole?

Letermovir and Voriconazole have a contraindicated drug interaction according to U.S. FDA drug labeling data. Table 6: Effect of Other Drugs on Voriconazole Pharmacokinetics [see Clinical Pharmacology (12.3) ] Drug/Drug Class (Mechanism of Interaction by the Drug) Voriconazole Plasma Exposure (C max and AUC τ after 200 mg every 12 hours) Recommendations for Voriconazole Dosage Adjustment/Comments Rifampin and Rifabutin (CYP450 Induction) Significantly Reduced Contraindicated Efavirenz (400 mg every 24 hours) (CYP450 Induction) Significantly Reduced Contraindicated High-dose Ritonavir (400 mg every 12 hours) (CYP450 Induction) Significantly Reduced Contraindicated Low-dose Ritonavir (100 mg every 12 hours) (CYP450 Induction) Reduced Coadministration of voriconazole and low-dose ritonavir (100 mg every 12 hours) should be avoided, unless an assessment of the benefit/risk to the patient justifies the use of voriconazole Carbamazepine (CYP450 Induction) Not Studied In Vivo or In Vitro , but Likely to Result in Significant Reduction Contraindicated Long Acting Barbiturates (e.g., phenobarbital, mephobarbital) (CYP450 Induction) Not Studied In Vivo or In Vitro , but Likely to Result in Significant Reduction Contraindicated Phenytoin (CYP450 Induction) Significantly Reduced Increase voriconazole maintenance dose from 4 mg/kg to 5 mg/kg IV every12 hours Letermovir (CYP2C9/2C19 Induction) Reduced If concomitant administration of voriconazole with letermovir cannot be avoided, monitor for reduced effectiveness of voriconazole. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This information is based on official FDA drug labeling sourced from OpenFDA and the NIH National Library of Medicine.

Severity
Contraindicated
Letermovir Class
Cytomegalovirus DNA Terminase Complex Inhibitor
Voriconazole Class
Azole Antifungal
Management
Do not take together
Data Source
U.S. FDA via OpenFDA

What To Tell Your Doctor or Pharmacist

If you are taking Letermovir and your doctor is considering prescribing Voriconazole (or vice versa), make sure to:

  • Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
  • Ask whether the benefits of combining these medications outweigh the risks for your specific situation
  • Ask what symptoms to watch for that would indicate the interaction is causing problems
  • Ask about alternative medications that do not interact with your current regimen
  • Ask how frequently you should be monitored while these are co-prescribed
  • Never stop or change either medication without first consulting your healthcare provider
💊 Letermovir+💊 Voriconazole

Severity & Interaction Details

⛔
contraindicated
Avoid this combination
FDA labeling lists this pair as contraindicated. The risk outweighs the benefit in nearly all cases.
Severity scale
MinorContra
On record
Yes
Drug A class
Cytomegalovirus DNA Terminase Complex Inhibitor
Drug B class
Azole Antifungal
Source
FDA drug label - voriconazole

What this means in plain English

Table 6: Effect of Other Drugs on Voriconazole Pharmacokinetics [see Clinical Pharmacology (12.3) ] Drug/Drug Class (Mechanism of Interaction by the Drug) Voriconazole Plasma Exposure (C max and AUC τ after 200 mg every 12 hours) Recommendations for Voriconazole Dosage Adjustment/Comments Rifampin and Rifabutin (CYP450 Induction) Significantly Reduced Contraindicated Efavirenz (400 mg every 24 hours) (CYP450 Induction) Significantly Reduced Contraindicated High-dose Ritonavir (400 mg every 12 hours) (CYP450 Induction) Significantly Reduced Contraindicated Low-dose Ritonavir (100 mg every 12 hours) (CYP450 Induction) Reduced Coadministration of voriconazole and low-dose ritonavir (100 mg every 12 hours) should be avoided, unless an assessment of the benefit/risk to the patient justifies the use of voriconazole Carbamazepine (CYP450 Induction) Not Studied In Vivo or In Vitro , but Likely to Result in Significant Reduction Contraindicated Long Acting Barbiturates (e.g., phenobarbital, mephobarbital) (CYP450 Induction) Not Studied In Vivo or In Vitro , but Likely to Result in Significant Reduction Contraindicated Phenytoin (CYP450 Induction) Significantly Reduced Increase voriconazole maintenance dose from 4 mg/kg to 5 mg/kg IV every12 hours Letermovir (CYP2C9/2C19 Induction) Reduced If concomitant administration of voriconazole with letermovir cannot be avoided, monitor for reduced effectiveness of voriconazole.

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Data sourced from U.S. FDA drug labeling via openFDA and the NIH National Library of Medicine. For informational purposes only. Always consult your pharmacist or physician.