Letermovir Injection and Eliglustat: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Eliglustat
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 eliglustat exposure and an increased risk of cardiac arrhythmias from prolongation of the PR, QTc and/or QRS cardiac intervals
Interaction Deep Dive
Concomitant use with fluconazole (a moderate CYP3A4 inhibitor) increased eliglustat AUC 2.5 to 3.2-fold, while concomitant use with fluconazole plus terbinafine (a strong CYP2D6 inhibitor) increased eliglustat AUC 5-fold to 13.6-fold. Avoid coadministration of eliglustat with moderate CYP3A inhibitors, in patients with Gaucher disease type 1 (GD1) who are CYP2D6 intermediate or poor metabolizers. In patients with GD1 who are extensive CYP2D6 metabolizers, reduce the eliglustat dose to 84 mg once daily if used concomitantly with a moderate CYP3A4 inhibitor1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of eliglustat
Literature reports
2 reports — tap to read
a) In patients with Gaucher disease type 1, eliglustat use with the moderate CYP3A4 inhibitor, fluconazole, was predicted to cause a 2.8-fold increase in eliglustat Cmax and a 3.2-fold increase in AUC in extensive CYP2D6 metabolizers and 2.5- and 2.9-fold increases, respectively, in intermediate CYP2D6 metabolizers. In poor metabolizers taking eliglustat 84 mg/day, concomitant use of fluconazole was predicted to increase Cmax by 2.4-fold and AUC by 3-fold 1.
b) Among extensive CYP2D6 metabolizers with Gaucher disease type 1, simulations suggested that eliglustat Cmax would increase 10.2-fold and AUC would increase 13.6-fold with concomitant use of fluconazole (a moderate CYP3A4 inhibitor) plus terbinafine (a strong CYP2D6 inhibitor). Among intermediate CYP2D6 metabolizers, the predicted eliglustat Cmax and AUC was 4.2- and 5-fold higher, respectively, with concurrent use of fluconazole plus terbinafine 1.
Common questions
Can I take Letermovir Injection and Eliglustat together?
Increased eliglustat exposure and an increased risk of cardiac arrhythmias from prolongation of the PR, QTc and/or QRS cardiac intervals Always confirm with your pharmacist or prescriber before making any change.
How serious is the Letermovir Injection and Eliglustat 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 Letermovir Injection or Eliglustat 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 (1)
- Product Information: CERDELGA(R) oral capsules, eliglustat oral capsules. Genzyme Corporation (per FDA, Cambridge, MA, 2018. DailyMed
Keep reading about Eliglustat
Keep reading about Letermovir Injection
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