Drug interactions
Lapatinib + Nafcillin
Severity: Moderate
Lapatinib and Nafcillin: 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
Nafcillin is a CYP3A4 inducer that can lower lapatinib concentrations and reduce its efficacy. The effect is documented mainly for other CYP3A4 substrates.
What this interaction means in plain words
Lapatinib and Nafcillin 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.
Why it happens
Induction of CYP3A4 by nafcillin increases lapatinib clearance.
What to do
Prefer an alternative antibiotic when possible. If nafcillin is required, monitor for reduced lapatinib response and consider a dose increase per labeling for strong inducers only if the combination is 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 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 Nafcillin?
MediHelp rates the interaction as moderate. Lapatinib and Nafcillin 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. Nafcillin is a CYP3A4 inducer that can lower lapatinib concentrations and reduce its efficacy. The effect is documented mainly for other CYP3A4 substrates.
How serious is the interaction between Lapatinib and Nafcillin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Prefer an alternative antibiotic when possible. If nafcillin is required, monitor for reduced lapatinib response and consider a dose increase per labeling for strong inducers only if the combination is prolonged.
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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