Drug interactions
Lapatinib + Mavacamten
Severity: Major
Lapatinib and Mavacamten: major interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Lapatinib may raise mavacamten exposure via CYP3A4 inhibition, which can reduce left ventricular ejection fraction and cause heart failure.
What this interaction means in plain words
Lapatinib and Mavacamten can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Lapatinib belongs to Oncology; Mavacamten belongs to Cardiovascular.
Why it happens
Inhibition of CYP3A4 (and possibly CYP2C19-related) metabolism of mavacamten by lapatinib.
What to do
Monitor LVEF and Valsalva gradient closely, and adjust the mavacamten dose per labeling when starting or stopping lapatinib. Interrupt mavacamten if LVEF falls below the labeled threshold.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Lapatinib
- Dofetilide + Lapatinib Contraindicated
- Ibutilide + Lapatinib Contraindicated
- Lapatinib + Pimozide Contraindicated
- Lapatinib + Saquinavir Contraindicated
- Lapatinib + Thioridazine Contraindicated
- Adagrasib + Lapatinib Major
Other interactions of Mavacamten
- Apalutamide + Mavacamten Contraindicated
- Carbamazepine + Mavacamten Contraindicated
- Clarithromycin + Mavacamten Contraindicated
- Dexlansoprazole + Mavacamten Contraindicated
- Efavirenz + Mavacamten Contraindicated
- Enzalutamide + Mavacamten Contraindicated
Frequently asked questions
Can I take Lapatinib with Mavacamten?
MediHelp rates the interaction as major. Lapatinib and Mavacamten can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Lapatinib may raise mavacamten exposure via CYP3A4 inhibition, which can reduce left ventricular ejection fraction and cause heart failure.
How serious is the interaction between Lapatinib and Mavacamten?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor LVEF and Valsalva gradient closely, and adjust the mavacamten dose per labeling when starting or stopping lapatinib. Interrupt mavacamten if LVEF falls below the labeled threshold.
What other medicines interact with Lapatinib?
MediHelp also lists interactions of Lapatinib with, for example, Dofetilide, Ibutilide, Pimozide. The full list is on the Lapatinib page.
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