Drug interactions
Fluvoxamine + Tamoxifen
Severity: Moderate
Fluvoxamine 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
Fluvoxamine may reduce conversion of tamoxifen to its active metabolites, such as endoxifen, potentially lowering its anti-estrogenic effect. The clinical impact on breast cancer outcomes is uncertain but is a concern.
What this interaction means in plain words
Fluvoxamine 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.
Fluvoxamine belongs to Central Nervous System; Tamoxifen belongs to Endocrine.
Why it happens
Fluvoxamine inhibits CYP2C19, CYP3A4 and to a lesser degree CYP2D6, which are involved in tamoxifen bioactivation.
What to do
Prefer an antidepressant with little CYP2D6 inhibition, such as venlafaxine, escitalopram or mirtazapine, in patients taking tamoxifen. If fluvoxamine is necessary, review the need for it regularly.
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 Fluvoxamine
- Agomelatine + Fluvoxamine Contraindicated
- Alosetron + Fluvoxamine Contraindicated
- Fezolinetant + Fluvoxamine Contraindicated
- Fluvoxamine + Isocarboxazid Contraindicated
- Fluvoxamine + Mavacamten Contraindicated
- Fluvoxamine + Methylene blue 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 Fluvoxamine with Tamoxifen?
MediHelp rates the interaction as moderate. Fluvoxamine 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. Fluvoxamine may reduce conversion of tamoxifen to its active metabolites, such as endoxifen, potentially lowering its anti-estrogenic effect. The clinical impact on breast cancer outcomes is uncertain but is a concern.
How serious is the interaction between Fluvoxamine 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: Prefer an antidepressant with little CYP2D6 inhibition, such as venlafaxine, escitalopram or mirtazapine, in patients taking tamoxifen. If fluvoxamine is necessary, review the need for it regularly.
What other medicines interact with Fluvoxamine?
MediHelp also lists interactions of Fluvoxamine with, for example, Agomelatine, Alosetron, Fezolinetant. The full list is on the Fluvoxamine page.
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