Drug interactions
Fluoxetine + Lapatinib
Severity: Moderate
Fluoxetine and Lapatinib: moderate 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 can prolong the QT interval, and fluoxetine may add to this effect. Lapatinib is also a CYP3A4 substrate and fluoxetine has some CYP3A4 inhibitory effect, which may modestly raise lapatinib exposure.
What this interaction means in plain words
Fluoxetine and Lapatinib can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fluoxetine belongs to Central Nervous System; Lapatinib belongs to Oncology.
Why it happens
Additive QT prolongation, with possible minor CYP3A4 inhibition by fluoxetine's metabolite.
What to do
Obtain a baseline ECG and monitor periodically, and correct potassium and magnesium abnormalities. Consider an alternative antidepressant if QTc is significantly prolonged.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Fluoxetine
- Fluoxetine + Isocarboxazid Contraindicated
- Fluoxetine + Mavacamten Contraindicated
- Fluoxetine + Methylene blue Contraindicated
- Fluoxetine + Phenelzine Contraindicated
- Fluoxetine + Pimozide Contraindicated
- Fluoxetine + Rasagiline Contraindicated
Other interactions of Lapatinib
- Dofetilide + Lapatinib Contraindicated
- Ibutilide + Lapatinib Contraindicated
- Lapatinib + Pimozide Contraindicated
- Lapatinib + Saquinavir Contraindicated
- Lapatinib + Thioridazine Contraindicated
- Adagrasib + Lapatinib Major
Frequently asked questions
Can I take Fluoxetine with Lapatinib?
MediHelp rates the interaction as moderate. Fluoxetine and Lapatinib can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Lapatinib can prolong the QT interval, and fluoxetine may add to this effect. Lapatinib is also a CYP3A4 substrate and fluoxetine has some CYP3A4 inhibitory effect, which may modestly raise lapatinib exposure.
How serious is the interaction between Fluoxetine and Lapatinib?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Obtain a baseline ECG and monitor periodically, and correct potassium and magnesium abnormalities. Consider an alternative antidepressant if QTc is significantly prolonged.
What other medicines interact with Fluoxetine?
MediHelp also lists interactions of Fluoxetine with, for example, Isocarboxazid, Mavacamten, Methylene blue. The full list is on the Fluoxetine page.
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