Paroxetine and Tamoxifen interaction
Paroxetine and Tamoxifen: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Paroxetine (BRISDELLE) label · effective 2025-04-28
When tamoxifen is used for the treatment or prevention of breast cancer, weigh the likely benefit of BRISDELLE for treating moderate to severe VMS associated with menopause vs. the risk of possible decreased tamoxifen effectiveness, and consider avoiding the concomitant use of BRISDELLE.
Tamoxifen Reduced plasma concentrations of active tamoxifen metabolite Consider avoiding concomitant use of tamoxifen and BRISDELLE.
Tamoxifen: Efficacy of tamoxifen may be reduced when administered concomitantly with BRISDELLE ( 5.3 , 7.1 )
Potential Impact on Tamoxifen Efficacy Some studies have shown that the efficacy of tamoxifen, as measured by the risk of breast cancer relapse/mortality, may be reduced when concomitantly administered with paroxetine as a result of paroxetine’s irreversible inhibition of CYP2D6 and lower tamoxifen blood levels [see Drug Interactions ( 7.1 )] .
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.
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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.