Effects of CYP induction by rifampicin on tamoxifen exposure

Lisette Binkhorst*, Teun Gelder, Walter Loos, FE Jongh, Paul Hamberg, Inge Helmantel, Evert de Jonge, Agnes Jager, Caroline Seynaeve, Ron van Schaik, RHJ Mathijssen, Jaap Verweij

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

35 Citations (Scopus)


Tamoxifen undergoes biotransformation into several metabolites, including endoxifen. Differences in metabolism contribute to the interindividual variability in endoxifen concentrations, potentially affecting treatment efficacy. We evaluated the effects of cytochrome P450 (CYP) induction by rifampicin on the exposure levels of tamoxifen and its metabolites and found that coadministration of rifampicin resulted in markedly reduced (up to 86%, P ≤ 0.040) concentrations of tamoxifen and its metabolites. Given the extensive metabolism undergone by tamoxifen, several factors may have contributed to this effect. Similar drug-drug interactions may exist between tamoxifen and other strong CYP inducers.

Original languageEnglish
Pages (from-to)62-67
Number of pages6
JournalClinical Pharmacology & Therapeutics
Issue number1
Publication statusPublished - Jul 2012

Research programs

  • EMC MM-01-25-01
  • EMC MM-03-86-01
  • EMC MM-03-86-08
  • EMC MM-04-39-05
  • EMC OR-01-34-01


Dive into the research topics of 'Effects of CYP induction by rifampicin on tamoxifen exposure'. Together they form a unique fingerprint.

Cite this