Drug interactions
Fostemsavir + Lapatinib
Severity: Moderate
Fostemsavir and Lapatinib: 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
Fostemsavir's metabolite temsavir inhibits BCRP, which may increase lapatinib absorption and exposure. Both drugs can prolong the QT interval, with fostemsavir doing so mainly at supratherapeutic doses.
What this interaction means in plain words
Fostemsavir and Lapatinib 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.
Fostemsavir belongs to Anti Virals; Lapatinib belongs to Oncology.
Why it happens
Temsavir inhibits BCRP transport, raising lapatinib exposure, and both agents have additive QT-prolonging effects.
What to do
Obtain a baseline ECG and monitor ECG and electrolytes during combined use. Watch for lapatinib adverse effects.
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
Other interactions of Fostemsavir
- Apalutamide + Fostemsavir Contraindicated
- Carbamazepine + Fostemsavir Contraindicated
- Enzalutamide + Fostemsavir Contraindicated
- Fostemsavir + Mitotane Contraindicated
- Fostemsavir + Phenytoin Contraindicated
- Fostemsavir + Rifampicin Contraindicated
Frequently asked questions
Can I take Fostemsavir with Lapatinib?
MediHelp rates the interaction as moderate. Fostemsavir and Lapatinib 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. Fostemsavir's metabolite temsavir inhibits BCRP, which may increase lapatinib absorption and exposure. Both drugs can prolong the QT interval, with fostemsavir doing so mainly at supratherapeutic doses.
How serious is the interaction between Fostemsavir and Lapatinib?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Obtain a baseline ECG and monitor ECG and electrolytes during combined use. Watch for lapatinib adverse effects.
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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