Drug interactions
Lapatinib + Quizartinib
Severity: Major
Lapatinib and Quizartinib: 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
Quizartinib carries a boxed warning for QT prolongation, torsades de pointes and cardiac arrest, and lapatinib also lengthens the QT interval. Combining them can produce additive QTc prolongation and increases arrhythmia risk.
What this interaction means in plain words
Lapatinib and Quizartinib 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; Quizartinib belongs to Oncology.
Why it happens
Additive pharmacodynamic QT prolongation; lapatinib may also raise quizartinib exposure via weak CYP3A4 inhibition.
What to do
Avoid the combination if possible. If it is unavoidable, monitor ECGs frequently, keep potassium and magnesium normal, and reduce the quizartinib dose or interrupt it according to QTc thresholds in labeling.
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 Quizartinib
- Quizartinib + Thioridazine Contraindicated
- Quizartinib + Ziprasidone Contraindicated
- Alfuzosin + Quizartinib Major
- Amiodarone + Quizartinib Major
- Amitriptyline + Quizartinib Major
- Amobarbital + Quizartinib Major
Frequently asked questions
Can I take Lapatinib with Quizartinib?
MediHelp rates the interaction as major. Lapatinib and Quizartinib 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. Quizartinib carries a boxed warning for QT prolongation, torsades de pointes and cardiac arrest, and lapatinib also lengthens the QT interval. Combining them can produce additive QTc prolongation and increases arrhythmia risk.
How serious is the interaction between Lapatinib and Quizartinib?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination if possible. If it is unavoidable, monitor ECGs frequently, keep potassium and magnesium normal, and reduce the quizartinib dose or interrupt it according to QTc thresholds in labeling.
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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