Drug interactions
Itraconazole + Lapatinib
Severity: Major
Itraconazole and Lapatinib: major interaction.
Last updated Sources: US FDA label
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
Itraconazole can substantially raise lapatinib exposure. Higher lapatinib levels increase the risk of adverse effects such as diarrhea, hepatotoxicity and QT prolongation.
What this interaction means in plain words
Itraconazole and Lapatinib 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.
Itraconazole belongs to Anti Fungals; Lapatinib belongs to Oncology.
Why it happens
Itraconazole is a strong CYP3A4 inhibitor (and P-glycoprotein inhibitor) and reduces the metabolism of lapatinib, a CYP3A4 substrate.
What to do
Avoid the combination where possible and choose an antifungal with less CYP3A4 inhibition. If it cannot be avoided, reduce the lapatinib dose as per labeling and monitor for toxicity and QTc during and for about a week after stopping itraconazole.
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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References
Other interactions of Itraconazole
- Alfuzosin + Itraconazole Contraindicated
- Alprazolam + Itraconazole Contraindicated
- Avanafil + Itraconazole Contraindicated
- Conivaptan + Itraconazole Contraindicated
- Dihydroergotamine intranasal + Itraconazole Contraindicated
- Dihydroergotamine + Itraconazole 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 Itraconazole with Lapatinib?
MediHelp rates the interaction as major. Itraconazole and Lapatinib 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. Itraconazole can substantially raise lapatinib exposure. Higher lapatinib levels increase the risk of adverse effects such as diarrhea, hepatotoxicity and QT prolongation.
How serious is the interaction between Itraconazole and Lapatinib?
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 where possible and choose an antifungal with less CYP3A4 inhibition. If it cannot be avoided, reduce the lapatinib dose as per labeling and monitor for toxicity and QTc during and for about a week after stopping itraconazole.
What other medicines interact with Itraconazole?
MediHelp also lists interactions of Itraconazole with, for example, Alfuzosin, Alprazolam, Avanafil. The full list is on the Itraconazole page.
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