Drug interactions
Dacomitinib + Tamoxifen
Severity: Major
Dacomitinib and Tamoxifen: 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
Dacomitinib strongly inhibits CYP2D6, which converts tamoxifen to its active metabolite endoxifen. This may reduce tamoxifen efficacy rather than increase it.
What this interaction means in plain words
Dacomitinib and Tamoxifen 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.
Dacomitinib belongs to Oncology; Tamoxifen belongs to Endocrine.
Why it happens
Dacomitinib inhibits CYP2D6, reducing endoxifen formation.
What to do
Avoid the combination where possible, or consider an aromatase inhibitor alternative if appropriate for the patient.
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 Tamoxifen
- Amiodarone + Tamoxifen Major
- Anastrozole + Tamoxifen Major
- Bupropion + Tamoxifen Major
- Carbamazepine + Tamoxifen Major
- Cinacalcet + Tamoxifen Major
- Eliglustat + Tamoxifen Major
Other interactions of Dacomitinib
- Dacomitinib + Thioridazine Contraindicated
- Amitriptyline + Dacomitinib Major
- Atomoxetine + Dacomitinib Major
- Brexpiprazole + Dacomitinib Major
- Clomipramine + Dacomitinib Major
- Dacomitinib + Desipramine Major
Frequently asked questions
Can I take Dacomitinib with Tamoxifen?
MediHelp rates the interaction as major. Dacomitinib and Tamoxifen 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. Dacomitinib strongly inhibits CYP2D6, which converts tamoxifen to its active metabolite endoxifen. This may reduce tamoxifen efficacy rather than increase it.
How serious is the interaction between Dacomitinib and Tamoxifen?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination where possible, or consider an aromatase inhibitor alternative if appropriate for the patient.
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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