Tamoxifen/Selected Strong CYP2D6 Inhibitors Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

Certain medications may decrease the effect of tamoxifen by interfering with how the body activates tamoxifen.

What might happen:

Your tamoxifen may not work as well at preventing your breast cancer from returning.

What you should do about this interaction:

Let your healthcare professionals (e.g. doctor or pharmacist) know that you are using these products together. Your doctor may want to change your medicine.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.

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  • 2.Jin Y, Desta Z, Stearns V, Ward B, Ho H, Lee KH, Skaar T, Storniolo AM, Li L, Araba A, Blanchard R, Nguyen A, Ullmer L, Hayden J, Lemler S, Weinshilboum RM, Rae JM, Hayes DF, Flockhart DA. CYP2D6 genotype, antidepressant use, and tamoxifen metabolism during adjuvant breast cancer treatment. J Natl Cancer Inst 2005 Jan 5;97(1):30-9.
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  • 12.Soltamox (tamoxifen citrate) US prescribing information. Midatech Pharma US Inc. September 25, 2018.
  • 13.Paxil (paroxetine hydrochloride) US prescribing information. Apotex Technologies January, 2017.
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  • 26.This information is based on or an extract from the UW Metabolism and Transport Drug Interaction Database (DIDB) Platform, Copyright University of Washington 1999-2019..
  • 27.US Food and Drug Administration (FDA). Drug Development and Drug Interactions: Table of Substrates, Inhibitors and Inducers. Available at: https://www.fda.gov/drugs/drug-interactions-labeling/drug-development-and -drug-interactions-table-substrates-inhibitors-and-inducers. Updated 11/14/2017.
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CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.