Nafcillin Injection and Elbasvir: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Nafcillin Injection
Elbasvir
No brand names on record
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
Decreased elbasvir plasma concentrations and reduced elbasvir efficacy
Interaction Deep Dive
Concomitant use of elbasvir, a CYP3A substrate, with moderate CYP3A inducers is not recommended due to the potential for decreased elbasvir plasma concentrations leading to reduced therapeutic efficacy1.
Why it happens (mechanism)
Induction of CYP3A-mediated elbasvir metabolism
Common questions
Can I take Nafcillin Injection and Elbasvir together?
Decreased elbasvir plasma concentrations and reduced elbasvir efficacy Always confirm with your pharmacist or prescriber before making any change.
How serious is the Nafcillin Injection and Elbasvir 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Nafcillin Injection or Elbasvir 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: ZEPATIER(TM) oral tablets, elbasvir, grazoprevir oral tablets. Merck Sharp & Dohme Corp. (per manufacturer), Whitehouse Station, NJ, 2016. DailyMed
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