Thioridazine and Lefamulin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Thioridazine
No brand names on recordLefamulin
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, reduced efficacy of lefamulin and an increased risk of QT interval prolongation
Interaction Deep Dive
The concomitant use of thioridazine with drugs that cause QT interval prolongation, such as lefamulin is contraindicated, as coadministration may increase the risk of QT prolongation and serious ventricular arrhythmias2. If coadministered, monitor ECG during treatment. Coadministration of lefamulin and thioridazine (moderate CYP3A4 inducer) may also reduce lefamulin exposure and may also reduce efficacy of lefamulin 1.
Why it happens (mechanism)
Induction of CYP3A4-mediated metabolism of lefamulin; additive QT interval prolongation
Common questions
Can I take Thioridazine and Lefamulin together?
Reduced lefamulin exposure, reduced efficacy of lefamulin and an increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Thioridazine 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 Thioridazine 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 (2)
- 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
- Product Information: thioridazine HCl oral tablets, thioridazine HCl oral tablets. Sun Pharmaceutical Industries, Inc. (per DailyMed), Cranbury, NJ, 2014.
Keep reading about Thioridazine
Keep reading about Lefamulin
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