Mavacamten and Lefamulin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Mavacamten
Lefamulin
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 mavacamten exposure, an increased risk of mavacamten-related adverse effects, reduced CYP3A4 substrate exposure and reduced efficacy of CYP3A4 substrate
Interaction Deep Dive
Concomitant use of mavacamten with moderate CYP3A4 inhibitors that are also CYP3A4 substrates may increase mavacamten exposure and may increase the risk of adverse effects, may also reduce the exposure of these substrates. In patients on stable therapy with a moderate CYP3A4 inhibitor, initiate mavacamten at the usual starting dose of 5 mg orally once daily. In patients treated with mavacamten and initiation with a moderate CYP3A4 inhibitor is intended, reduce the mavacamten dose to the next lower daily (mg) dose level (ie, 15 mg to 10 mg; 10 mg to 5 mg; 5 mg to 2.5 mg). Schedule clinical and echocardiographic assessment 4 weeks after inhibitor initiation, and do not up-titrate to the next higher daily (mg) dose level of mavacamten until 12 weeks after inhibitor initiation. In patients on a stable mavacamten dose of 2.5 mg/day, avoid initiation of a concomitant moderate CYP3A4 inhibitor (because a lower dose is not available). For short-term use (eg, 1 week), interrupt mavacamten for the duration of treatment with a moderate CYP3A4 inhibitor. Mavacamten may be reinitiated at the previous dose immediately on discontinuation of concomitant therapy. Closely monitor when mavacamten is used in combination with CYP3A4 substrates where reduction in the exposure of these substrates may reduce their activity1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of mavacamten; induction of CYP3A4-substrate metabolism by mavacamten
Literature reports
2 reports — tap to read
a) Concomitant use of mavacamten 25 mg with verapamil (a moderate CYP3A4 inhibitor) sustained release 240 mg increased mavacamten AUC(inf) by 15% and Cmax by 52% in CYP2C19 normal and intermediate metabolizers. Concomitant use of mavacamten with dilTIAZem (a moderate CYP3A4 inhibitor) in CYP2C19 poor metabolizers is predicted to increase mavacamten AUC(0 to 24 hours) up to 55% and Cmax up to 42% 1.
b) Concomitant use of a 16-day course of mavacamten (25 mg on days 1 and 2, followed by 15 mg for 14 days) resulted in a 13% and 7% decrease in midazolam (a CYP3A4 substrate) AUC(inf) and Cmax, respectively, in healthy subjects. Following coadministration of mavacamten once daily in hypertrophic cardiomyopathy patients, midazolam AUC(inf) and Cmax are predicted to decrease by 45% and 24%, respectively 1.
Common questions
Can I take Mavacamten and Lefamulin together?
Increased mavacamten exposure, an increased risk of mavacamten-related adverse effects, reduced CYP3A4 substrate exposure and reduced efficacy of CYP3A4 substrate Always confirm with your pharmacist or prescriber before making any change.
How serious is the Mavacamten 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 "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Mavacamten 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: CAMZYOS(R) oral capsules, mavacamten oral capsules. Bristol-Myers Squibb Company (per Manufacturer), Princeton, NJ, 2025. DailyMed
Keep reading about Mavacamten
Keep reading about Lefamulin
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Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
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