Ivacaftor and Letermovir Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ivacaftor
Letermovir Injection
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased ivacaftor exposure
Interaction Deep Dive
The concomitant use of ivacaftor with the moderate CYP3A inhibitor fluconazole increased ivacaftor AUC by 3-fold. Dose adjustments are required for the concomitant use of ivacaftor or ivacaftor-containing products with moderate CYP3A inhibitors. For Kalydeco(R), reduce the dose to 150 mg orally once daily (6 years or older), or 25 mg (weight, 5 kg to less than 7 kg), 50 mg (7 kg to less than 14 kg) or 75 mg (14 kg or greater) of oral granules once daily in patients 6 months to less than 6 years; concomitant use is not recommended in patients younger than 6 months2. For Symdeko(TM), alternate daily dosing starting with tezacaftor 100 mg/ivacaftor 150 mg orally in the morning on day 1, then ivacaftor 150 mg orally in the morning on day 2 3. For Trikafta(TM), alternate daily dosing starting with 2 tablets (elexacaftor 100 mg/tezacaftor 50 mg/ivacaftor 75 mg per tablet) orally in the morning on day 1, then ivacaftor 150 mg orally in the morning on day 2. Continue alternating without evening doses 1. No dose adjustment is required for concomitant use of Orkambi(R) 4.
Why it happens (mechanism)
Inhibition of CYP3A-mediated metabolism of ivacaftor
Literature reports
2 reports — tap to read
a) Simulations indicated that coadministration with moderate CYP3A inhibitors may increase elexacaftor and tezacaftor AUC by approximately 1.9 to 2.3-fold and 2.1-fold, respectively 1.
b) Coadministration of ivacaftor 150 mg orally twice daily with moderate CYP3A inhibitor fluconazole 400 mg orally x 1 dose on day 1, followed by 200 mg once daily resulted in a 2.95-fold increase in ivacaftor exposure and a 2.47-fold increase in Cmax 31.
Common questions
Can I take Ivacaftor and Letermovir Injection together?
Increased ivacaftor exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ivacaftor and Letermovir Injection interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Ivacaftor or Letermovir Injection need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (4)
- Product Information: TRIKAFTA(R) oral tablets oral granules, elexacaftor, tezacaftor, ivacaftor oral tablets oral granules; ivacaftor oral tablets oral granules. Vertex Pharmaceuticals Incorporated (per FDA), Boston, MA, 2024. DailyMed
- Product Information: KALYDECO(R) oral tablets, oral granules, ivacaftor oral tablets, oral granules. Vertex Pharmaceuticals Incorporated (per FDA), Boston, MA, 2023. DailyMed
- Product Information: SYMDEKO(TM) oral tablets, tezacaftor ivacaftor oral tablets and ivacaftor oral tablets. Vertex Pharmaceuticals Incorporated (per manufacturer), Boston, MA, 2018. DailyMed
- Product Information: ORKAMBI(R) oral tablets, lumacaftor ivacaftor oral tablets. Vertex Pharmaceuticals Incorporated (per manufacturer), Boston, MA, 2016. DailyMed
Keep reading about Ivacaftor
Keep reading about Letermovir Injection
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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