Drug interactions
Tamoxifen + Venlafaxine
Severity: Minor
Tamoxifen and Venlafaxine: minor 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
Tamoxifen needs CYP2D6 to be converted into endoxifen, its most active metabolite. Venlafaxine is only a weak CYP2D6 inhibitor, so any reduction in endoxifen is small and the effect on breast cancer outcomes is uncertain.
What this interaction means in plain words
Tamoxifen and Venlafaxine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Tamoxifen belongs to Endocrine; Venlafaxine belongs to Central Nervous System.
Why it happens
Weak inhibition of CYP2D6 by venlafaxine, which may slightly reduce the formation of endoxifen from tamoxifen.
What to do
Venlafaxine is generally considered an acceptable antidepressant or hot-flash treatment during tamoxifen therapy. Strong CYP2D6 inhibitors such as paroxetine and fluoxetine should be avoided instead.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Venlafaxine
- Isocarboxazid + Venlafaxine Contraindicated
- Methylene blue + Venlafaxine Contraindicated
- Phenelzine + Venlafaxine Contraindicated
- Procarbazine + Venlafaxine Contraindicated
- Rasagiline + Venlafaxine Contraindicated
- Safinamide + Venlafaxine Contraindicated
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 Tamoxifen with Venlafaxine?
MediHelp rates the interaction as minor. Tamoxifen and Venlafaxine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Tamoxifen needs CYP2D6 to be converted into endoxifen, its most active metabolite. Venlafaxine is only a weak CYP2D6 inhibitor, so any reduction in endoxifen is small and the effect on breast cancer outcomes is uncertain.
How serious is the interaction between Tamoxifen and Venlafaxine?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Venlafaxine is generally considered an acceptable antidepressant or hot-flash treatment during tamoxifen therapy. Strong CYP2D6 inhibitors such as paroxetine and fluoxetine should be avoided instead.
What other medicines interact with Venlafaxine?
MediHelp also lists interactions of Venlafaxine with, for example, Isocarboxazid, Methylene blue, Phenelzine. The full list is on the Venlafaxine page.
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