Drug interactions
Lapatinib + Saquinavir
Severity: Contraindicated
Lapatinib and Saquinavir: contraindicated 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
Saquinavir, usually boosted with ritonavir, is a strong CYP3A4 inhibitor that can greatly raise lapatinib exposure. Both drugs prolong the QT interval, so the risk of torsades de pointes and lapatinib toxicity increases.
What this interaction means in plain words
Lapatinib and Saquinavir are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Why it happens
Saquinavir inhibits CYP3A4 metabolism of lapatinib, with additive QT prolongation.
What to do
Avoid the combination and choose an alternative antiretroviral or kinase inhibitor. If it cannot be avoided, reduce lapatinib dose substantially and monitor ECG closely.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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Other interactions of Lapatinib
- Dofetilide + Lapatinib Contraindicated
- Ibutilide + Lapatinib Contraindicated
- Lapatinib + Pimozide Contraindicated
- Lapatinib + Thioridazine Contraindicated
- Adagrasib + Lapatinib Major
- Amiodarone + Lapatinib Major
Frequently asked questions
Can I take Lapatinib with Saquinavir?
MediHelp rates the interaction as contraindicated. Lapatinib and Saquinavir are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Saquinavir, usually boosted with ritonavir, is a strong CYP3A4 inhibitor that can greatly raise lapatinib exposure. Both drugs prolong the QT interval, so the risk of torsades de pointes and lapatinib toxicity increases.
How serious is the interaction between Lapatinib and Saquinavir?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination and choose an alternative antiretroviral or kinase inhibitor. If it cannot be avoided, reduce lapatinib dose substantially and monitor ECG closely.
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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