Drug interactions
Lenacapavir + Tamoxifen
Severity: Moderate
Lenacapavir and Tamoxifen: 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
Lenacapavir is a moderate CYP3A inhibitor and may increase tamoxifen concentrations, with the effect persisting for months after subcutaneous dosing. Higher tamoxifen exposure may increase adverse effects, though its clinical consequence is uncertain.
What this interaction means in plain words
Lenacapavir and Tamoxifen 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.
Lenacapavir belongs to Anti Virals; Tamoxifen belongs to Endocrine.
Why it happens
Lenacapavir inhibits CYP3A4, reducing tamoxifen metabolism.
What to do
Monitor for tamoxifen adverse effects, including thromboembolic events and hot flushes, during and for months after lenacapavir exposure.
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 Tamoxifen
- Amiodarone + Tamoxifen Major
- Anastrozole + Tamoxifen Major
- Bupropion + Tamoxifen Major
- Carbamazepine + Tamoxifen Major
- Cinacalcet + Tamoxifen Major
- Dacomitinib + Tamoxifen Major
Other interactions of Lenacapavir
- Apalutamide + Lenacapavir Contraindicated
- Carbamazepine + Lenacapavir Contraindicated
- Enzalutamide + Lenacapavir Contraindicated
- Flibanserin + Lenacapavir Contraindicated
- Lenacapavir + Phenytoin Contraindicated
- Lenacapavir + Rifampicin Contraindicated
Frequently asked questions
Can I take Lenacapavir with Tamoxifen?
MediHelp rates the interaction as moderate. Lenacapavir and Tamoxifen 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. Lenacapavir is a moderate CYP3A inhibitor and may increase tamoxifen concentrations, with the effect persisting for months after subcutaneous dosing. Higher tamoxifen exposure may increase adverse effects, though its clinical consequence is uncertain.
How serious is the interaction between Lenacapavir and Tamoxifen?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for tamoxifen adverse effects, including thromboembolic events and hot flushes, during and for months after lenacapavir exposure.
What other medicines interact with Tamoxifen?
MediHelp also lists interactions of Tamoxifen with, for example, Amiodarone, Anastrozole, Bupropion. The full list is on the Tamoxifen page.
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