Quinidine and Lefamulin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Lefamulin
Quinidine
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 lefamulin exposure, an increased risk of lefamulin-related adverse reactions, increased sensitive CYP3A4 substrate exposure and an increased risk of QT interval prolongation and torsades de pointes
Interaction Deep Dive
Oral lefamulin is contraindicated with sensitive CYP3A4 substrates that prolong the QT interval, as it may result in increased sensitive CYP3A4 substrates exposure, leading to QT prolongation and cases of torsades de pointes. Concomitant use of IV lefamulin with sensitive CYP3A4 substrates does not affect the exposure of CYP3A4 substrates. Additionally, concomitant use of oral lefamulin with P-gp inhibitors may increase risk of lefamulin exposure and may also increase lefamulin-related adverse reactions1.
Why it happens (mechanism)
Inhibition of P-gp-mediated efflux transport of lefamulin; inhibition of CYP3A4 substrate-mediated metabolism by lefamulin; additive QT interval prolongation
Literature reports
1 report — tap to read
a) In a drug interaction study, mean AUC and Cmax of midazolam (sensitive CYP3A4 substrate) were increased by approximately 200% and 100%, respectively, when oral midazolam was administered concomitantly with and at 2 or 4 hours after administration of oral lefamulin 1.
Common questions
Can I take Quinidine and Lefamulin together?
Increased lefamulin exposure, an increased risk of lefamulin-related adverse reactions, increased sensitive CYP3A4 substrate exposure and an increased risk of QT interval prolongation and torsades de pointes Always confirm with your pharmacist or prescriber before making any change.
How serious is the Quinidine and Lefamulin interaction?
It is rated contraindicated. These should generally not be used together.
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 Quinidine 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
Keep reading about Lefamulin
Keep reading about Quinidine
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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