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Dec 4, 2007 08:22AM
This article says that in their study, the half life of tamoxifen and its N-desmethyltamoxifen metabolite was 9 and 13 days respectively. This study was BEFORE the interaction/genetics study, so we don't know how variable these values really are, but in this study, it would take 9 days for the blood tamoxifen levels to decrease by one-half.
I don't think you missed too much by missing your dose. I'm sure there have been others who have missed a dose, Lynn.
1: Cancer Epidemiol Biomarkers Prev. 2001 Sep;10(9):967-70. Links
Correlation between tamoxifen elimination and biomarker recovery in a primary prevention trial.
Guerrieri-Gonzaga A, Baglietto L, Johansson H, Bonanni B, Robertson C, Sandri MT, Canigiula L, Lampreda C, Diani S, Lien EA, Decensi A.
Division of Chemoprevention, European Institute of Oncology, 20141 Milan, Italy.
We have shown previously that a reduction from the conventional dose of tamoxifen is associated with a comparable modulation of circulating biomarkers, including insulin-like growth factor-I and cholesterol. In the present study, we have correlated serum tamoxifen elimination with biomarker recovery in healthy subjects completing a 5-year intervention period. Tamoxifen, N-desmethyltamoxifen, and biomarker levels were measured at 0 (baseline), 2, 4, and 6 weeks after completion of treatment in 23 healthy postmenopausal women allocated to tamoxifen 20 mg/day and in 6 women allocated to placebo. Mean (+/-SD) serum tamoxifen and N-desmethyltamoxifen concentrations were, respectively, 141 +/- 50 and 226 +/- 77 ng/ml at baseline, 36 +/- 19 and 99 +/- 46 at 2 weeks, 20 +/- 15 and 61 +/- 37 at 4 weeks, and 12 +/- 9 and 36 +/- 26 at 6 weeks. Serum tamoxifen and N-desmethyltamoxifen half-lives were 9 and 13 days, respectively. Body mass index was associated positively with drug's serum half-life. Compared with baseline values, the percentage increase in total cholesterol, low-density lipoprotein cholesterol, and insulin-like growth factor-I 4 weeks after treatment completion was 5, 9, and 14%, respectively. No change during the 6-week period was observed in the placebo arm. Our findings indicate that the biomarker recovery is slower than serum tamoxifen elimination, suggesting that low tamoxifen concentrations may still exert a biological effect. In addition, the prolonged half-life of tamoxifen and metabolite provides the rationale for a weekly administration of the drug in a preventive context. However, the clinical implications of our findings remain to be defined.
PMID: 11535549 [PubMed - indexed for MEDLINE]
Classic LCIS.If knowledge can create problems, it is not through ignorance that we can solve them- Isaac Asimov
12/8/2005, LCIS, ER+/PR-
1/24/2006 Lumpectomy: Left
7/15/2006 Tamoxifen pills (Nolvadex, Apo-Tamox, Tamofen, Tamone)