Nafcillin Injection and Lefamulin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Lefamulin
Nafcillin 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
Reduced lefamulin exposure and reduced efficacy of lefamulin
Interaction Deep Dive
Avoid coadministration of lefamulin with strong or moderate CYP3A4 inducers unless the benefit outweighs the risks, as it may reduce lefamulin exposure and may also reduce efficacy of lefamulin. In a drug interaction study, oral rifAMPin (strong inducer) reduced the mean lefamulin AUC(0-inf) and Cmax by 28% and 8%, respectively, when administered concomitantly with lefamulin injection. Additionally, oral rifAMPin reduced the mean lefamulin AUC(0-inf) and Cmax by 72% and 57%, respectively, when administered concomitantly with lefamulin tablets1.
Why it happens (mechanism)
Induction of CYP3A4-mediated metabolism of lefamulin
Literature reports
1 report — tap to read
a) In a drug interaction study, oral rifAMPin (strong inducer) reduced the mean lefamulin AUC(0-inf) and Cmax by 28% and 8%, respectively, when administered concomitantly with lefamulin injection. Additionally, oral rifAMPin reduced the mean lefamulin AUC(0-inf) and Cmax by 72% and 57%, respectively, when administered concomitantly with lefamulin tablets 1.
Common questions
Can I take Nafcillin Injection and Lefamulin together?
Reduced lefamulin exposure and reduced efficacy of lefamulin Always confirm with your pharmacist or prescriber before making any change.
How serious is the Nafcillin Injection and Lefamulin 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 Lefamulin 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: XENLETA(R) oral tablets, intravenous injection, lefamulin oral tablets, intravenous injection. Nabriva Therapeutics US Inc (per FDA), King of Prussia, PA, 2021. DailyMed
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