2019
DOI: 10.1186/s40360-019-0358-y
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Hormonal status affects plasma exposure of tamoxifen and its main metabolites in tamoxifen-treated breast cancer patients

Abstract: BackgroundTamoxifen is considered a prodrug of its active metabolite endoxifen, which is dependent on the CYP2D6 and CYP3A enzymes. Tamoxifen pharmacokinetic variability influences endoxifen exposure and, consequently, its clinical outcome. This study investigated the impact of hormonal status on the pharmacokinetics of tamoxifen and its metabolites in TAM-treated breast cancer patients.MethodsTAM-treated breast cancer patients (n = 40) previously believed to have CYP3A activity within the normal range based o… Show more

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Cited by 18 publications
(24 citation statements)
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“…For the reference formulation (phase 2), for example, interindividual variation was 5.3‐fold for tamoxifen, 5.6‐fold for endoxifen and 4.1‐fold for 4OHT. The range of plasma concentrations of the three compounds is within the range reported for Brazilians and other populations . ANOVA statistics showed no significant differences in plasma concentrations of tamoxifen or any of its metabolites across the three study phases.…”
Section: Resultssupporting
confidence: 72%
“…For the reference formulation (phase 2), for example, interindividual variation was 5.3‐fold for tamoxifen, 5.6‐fold for endoxifen and 4.1‐fold for 4OHT. The range of plasma concentrations of the three compounds is within the range reported for Brazilians and other populations . ANOVA statistics showed no significant differences in plasma concentrations of tamoxifen or any of its metabolites across the three study phases.…”
Section: Resultssupporting
confidence: 72%
“…The effect of menopausal status on the PK of drugs has been poorly investigated. The pre-menopausal status has been associated with decreased endoxifen plasma concentrations by 135% compared to post-menopausal status in tamoxifen-treated breast cancer patients phenotyped as NMs for CYP2D6 and with CYP3A activity [ 111 ]. The authors hypothesized that a lower P-gp activity in the gut of post-menopausal patients could be held responsible for the increased tamoxifen bioavailability.…”
Section: Potential Drug-pathophysiological Interactionsmentioning
confidence: 99%
“…Concurrent medication inhibiting or inducing CYP2D6 enzymatic activity are known to affect endoxifen concentrations and therefore are of clinical value. Nonetheless, with this knowledge, the onedose-ts-all strategy is still current practice (10,12,16,(19)(20)(21)(22)(23).…”
Section: Introductionmentioning
confidence: 99%