Drug interactions
Lapatinib + Nelfinavir
Severity: Major
Lapatinib and Nelfinavir: 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
Nelfinavir inhibits CYP3A4 and can increase lapatinib exposure, raising the risk of diarrhea, hepatotoxicity and QT prolongation. Lapatinib may also modestly increase nelfinavir through CYP3A4 and P-gp inhibition.
What this interaction means in plain words
Lapatinib and Nelfinavir 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; Nelfinavir belongs to Anti Virals.
Why it happens
Nelfinavir inhibits CYP3A4 metabolism of lapatinib, and lapatinib inhibits CYP3A4 and P-gp, affecting nelfinavir.
What to do
Avoid combining where possible; if necessary, reduce the lapatinib dose as advised in labeling for strong CYP3A4 inhibitors and monitor ECG, liver tests and toxicity.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Lapatinib and Nelfinavir, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
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 Nelfinavir
- Alfuzosin + Nelfinavir Contraindicated
- Avanafil + Nelfinavir Contraindicated
- Dronedarone + Nelfinavir Contraindicated
- Eletriptan + Nelfinavir Contraindicated
- Ergotamine + Nelfinavir Contraindicated
- Flibanserin + Nelfinavir Contraindicated
Frequently asked questions
Can I take Lapatinib with Nelfinavir?
MediHelp rates the interaction as major. Lapatinib and Nelfinavir 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. Nelfinavir inhibits CYP3A4 and can increase lapatinib exposure, raising the risk of diarrhea, hepatotoxicity and QT prolongation. Lapatinib may also modestly increase nelfinavir through CYP3A4 and P-gp inhibition.
How serious is the interaction between Lapatinib and Nelfinavir?
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 combining where possible; if necessary, reduce the lapatinib dose as advised in labeling for strong CYP3A4 inhibitors and monitor ECG, liver tests and toxicity.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
