The Fall Guy (2)

Fatal Forty DDI: tamoxifen, diphenhydramine, CYP2D6
  • Catherine Marcucci
  • Neil B. Sandson


This case discusses the interaction of tamoxifen and diphenhydramine. Tamoxifen is a cytochrome P450 2D6 prodrug substrate and diphenhydramine is a 2D6 inhibitor.


Pharmacokinetic Prodrug Inhibitor Tamoxifen N-desmethyltamoxifen 4-hydroxy-n-desmethytamoxifen Endoxifen Benadryl Diphenhydramine Cytochrome P450 CYP 2D6 CYP2D 


  1. 1.
    Akutsu T, Kobayashi K, Sakurada K, et al. Identification of human cytochrome p450 isozymes involved in diphenhydramine N-demethylation. Drug Metab Dispos. 2007;35(1):72–8.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  1. 1.Anesthesia Services DepartmentPhiladelphia Veterans Affairs Medical CenterPhiladelphiaUSA
  2. 2.Department of PsychiatryUniversity of Maryland Medical SystemBaltimoreUSA
  3. 3.Department of PsychiatryVA Maryland Health Care SystemBaltimoreUSA

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