Tamoxifen metabolites in patients on long-term adjuvant therapy for breast cancer.

Abstract

Serum concentrations of tamoxifen, 4-OH-tamoxifen, N-desmethyltamoxifen, and metabolites E and Y were assayed to assess the variation of tamoxifen-metabolism during short-term and long-term endocrine treatment for breast cancer. Once steady-state was achieved, serum levels of tamoxifen and its metabolites in individual patients were stable in the short (10 weeks) and long term (over 7 years) (coefficient of variation [CV], 10-15%), but the variation between individuals (CV 50-70%) was high. Serum tamoxifen and N-desmethyltamoxifen levels were not correlated with indices of obesity. Thus this does not explain the large variation between individuals. In addition to the metabolites that were measured, 4-hydroxy-N-desmethyltamoxifen was tentatively identified in patients' serum. Overall, this study demonstrated that the metabolites of tamoxifen are stable (i.e. no metabolic tolerance) for up to 10 years of drug administration.

• Authors: S M Langan-Fahey, D C Tormey, V C Jordan
• Journal: European journal of cancer (Oxford, England : 1990) (Eur J Cancer) Vol. 26 Issue 8 Pg. 883-8 ( 1990) ISSN: 0959-8049 [Print] England
• PMID: 2145931 (Publication Type: Journal Article)

Chemical References

• Estrogen Antagonists
• Tamoxifen
• afimoxifene
• ICI 142269
• N-desmethyltamoxifen

Topics

• Breast Neoplasms (drug therapy)
• Drug Stability
• Estrogen Antagonists (blood)
• Humans
• Tamoxifen (administration & dosage, analogs & derivatives, blood, metabolism, therapeutic use)
• Time Factors