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Tamoxifen therapy reduced platelet counts without change in platelet function
Author(s) -
Jin Y.,
Ward B.,
Storniolo A.,
Desta Z.,
Nguyen A.,
Hayes D.,
Stearns V.,
Flockhart D. A.
Publication year - 2005
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1016/j.clpt.2004.12.133
Subject(s) - tamoxifen , platelet , medicine , pharmacology , prospective cohort study , endocrinology , breast cancer , cancer
Background/Aims Tamoxifen therapy can cause a 4% decrease in platelet count, yet increases risk of thrombosis. We hypothesized that this decrease was influenced by concentrations of tamoxifen or its metabolites that may lead to changes in platelet function. Methods Candidates for tamoxifen therapy (n=88) participated in a prospective, observational trial. Before and 4 months after tamoxifen treatment, we measured platelet counts (N=88), platelet aggregation (N=17), and plasma concentrations of tamoxifen and its metabolites (N=41). Results Tamoxifen therapy led to a 4% decrease in platelet counts (P= 0.039) in our cohort. This decrease was negatively correlated with plasma concentrations of endoxifen (R 2 = 0.27, P=0.0006) and 4‐hydroxy tamoxifen (R 2 = 0.22, P=0.003), but not with tamoxifen and N‐desmethyl tamoxifen. There were no significant changes in either ADP (13.33±12.3 Ω vs 11.6±11.5 Ω, P= 0.12) or arachadonic acid (9.6±46.1 vs 7.0±37.6 Ω, P=0.19) induced platelet aggregation. Conclusion Decrease in platelet counts after tamoxifen was negatively correlated with endoxifen and 4‐hydroxy tamoxifen concentrations, and did not lead to changes in platelet function. Clinical Pharmacology & Therapeutics (2005) 77 , P63–P63; doi: 10.1016/j.clpt.2004.12.133