Fluoxetine and Tamoxifen: Drug Interaction Guide
Quick answer: This is a major interaction — avoid combining Fluoxetine and Tamoxifen unless specifically directed by your doctor.
How Fluoxetine interacts with Tamoxifen
Fluoxetine is a strong CYP2D6 inhibitor and reduces conversion of tamoxifen to its active metabolite endoxifen, potentially decreasing breast cancer recurrence-free survival.
What you should do
Choose a non-CYP2D6-inhibiting antidepressant (e.g., venlafaxine, citalopram, escitalopram) for patients on tamoxifen for breast cancer.
Key facts
Severity
Major — avoid combination
Mechanism
Fluoxetine is a strong CYP2D6 inhibitor and reduces conversion of tamoxifen to its active metabolite endoxifen, potentia...
Action
Choose a non-CYP2D6-inhibiting antidepressant (e.g., venlafaxine, citalopram, escitalopram) for patients on tamoxifen fo...
Frequently asked questions
Can I take Fluoxetine and Tamoxifen together?
No — this combination should generally be avoided. Choose a non-CYP2D6-inhibiting antidepressant (e.g., venlafaxine, citalopram, escitalopram) for patients on tamoxifen for breast cancer.
What is the severity of this interaction?
The interaction between Fluoxetine and Tamoxifen is classified as Major — avoid combination. Fluoxetine is a strong CYP2D6 inhibitor and reduces conversion of tamoxifen to its active metabolite endoxifen, potentially decreasing breast cancer recurrence-free survival.
What should I do if I'm prescribed both?
Choose a non-CYP2D6-inhibiting antidepressant (e.g., venlafaxine, citalopram, escitalopram) for patients on tamoxifen for breast cancer. Always consult your prescribing clinician — do not stop or change medications without medical guidance.
Last reviewed: by iMedic Medical Editorial Team. Our editorial process.