Paroxetine and Tamoxifen interaction
Paroxetine and Tamoxifen: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Paroxetine (PAROXETINE HYDROCHLORIDE) label · effective 2026-09-16
Reduction of Efficacy of Tamoxifen Some studies have shown that the efficacy of tamoxifen, as measured by the risk of breast cancer relapse/mortality, may be reduced with concomitant use of paroxetine as a result of paroxetine’s irreversible inhibition of CYP2D6 and lower blood levels of tamoxifen [see Drug Interactions ( 7.1 )].
When tamoxifen is used for the treatment or prevention of breast cancer, prescribers should consider using an alternative antidepressant with little or no CYP2D6 inhibition.
Concomitant use with Tamoxifen: Consider use of an alternative antidepressant with little or no CYP2D6 inhibition.
Tamoxifen Clinical Impact Concomitant use of tamoxifen with Paroxetine HCL CR may lead to reduced plasma concentrations of the active metabolite (endoxifen) and reduced efficacy of tamoxifen Intervention Consider use of an alternative antidepressant little or no CYP2D6 inhibition [see Warnings and Precautions ( 5.11 )].
From the Tamoxifen (SOLTAMOX) label · effective 2021-11-29
Strong Inhibitors of CYP2D6 The impact on the efficacy of tamoxifen with co-administration of strong CYP2D6 inhibitors (e.g., paroxetine) is not well established.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.