Drug interactions
Lumacaftor / ivacaftor + Tamoxifen
Severity: Moderate
Lumacaftor / ivacaftor 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
Lumacaftor is a strong CYP3A inducer and may lower tamoxifen and active metabolite concentrations, potentially reducing efficacy. Effects on CYP2C9 are mixed, making the net result uncertain.
What this interaction means in plain words
Lumacaftor / ivacaftor 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.
Why it happens
Lumacaftor induces CYP3A4 and CYP2C9, increasing tamoxifen clearance.
What to do
Monitor for reduced tamoxifen response and consider an alternative endocrine therapy if long-term co-administration is required.
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
Frequently asked questions
Can I take Lumacaftor / ivacaftor with Tamoxifen?
MediHelp rates the interaction as moderate. Lumacaftor / ivacaftor 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. Lumacaftor is a strong CYP3A inducer and may lower tamoxifen and active metabolite concentrations, potentially reducing efficacy. Effects on CYP2C9 are mixed, making the net result uncertain.
How serious is the interaction between Lumacaftor / ivacaftor 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 reduced tamoxifen response and consider an alternative endocrine therapy if long-term co-administration is required.
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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