Drug interactions
Lapatinib + Phenobarbital
Severity: Major
Lapatinib and Phenobarbital: 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
Phenobarbital induces CYP3A4 and P-gp and can substantially reduce lapatinib exposure, potentially compromising cancer treatment. Effects persist after phenobarbital discontinuation.
What this interaction means in plain words
Lapatinib and Phenobarbital 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.
Why it happens
Induction of CYP3A4 and P-gp increases lapatinib clearance.
What to do
Switch to a non-inducing anticonvulsant if possible. If it must continue, lapatinib dose titration per labeling for strong inducers with close monitoring is needed, then reduce the dose after phenobarbital is stopped.
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
Frequently asked questions
Can I take Lapatinib with Phenobarbital?
MediHelp rates the interaction as major. Lapatinib and Phenobarbital 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. Phenobarbital induces CYP3A4 and P-gp and can substantially reduce lapatinib exposure, potentially compromising cancer treatment. Effects persist after phenobarbital discontinuation.
How serious is the interaction between Lapatinib and Phenobarbital?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Switch to a non-inducing anticonvulsant if possible. If it must continue, lapatinib dose titration per labeling for strong inducers with close monitoring is needed, then reduce the dose after phenobarbital is stopped.
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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