RESUMEN
BACKGROUND: Adjuvant treatment with the estrogen receptor modulator tamoxifen is a well established long-term therapy in breast cancer. This study investigated the effect of tamoxifen on blood pressure (BP) and on factors by which it might be influenced. METHODS: Normotensive postmenopausal women on > 12 months adjuvant tamoxifen therapy were randomized to withdraw or continue tamoxifen for 6 weeks and then to crossover to the alternative regimen for a second 6-week period. Measurements of clinic and ambulatory BP, plasma renin activity (PRA), and fractional sodium excretion (FE(Na)) were performed at baseline and at the end of each study period. RESULTS: Twenty-three women completed the study (mean age 60.6 +/- 8.3 years). There was no effect of tamoxifen on clinic BP (mean difference between withdrawal and continuation for systolic BP, 0.4 +/- 8.4 mm Hg, 95% confidence interval [CI] -4.0 to 3.2, and diastolic 0.6 +/- 4.7, 95%CI -1.4 to 2.7) or 24-hour ambulatory BP (systolic 0.7 +/- 7.4 mmHg, 95%CI -2.6 to 3.9; diastolic BP, 1.9 +/- 5.5, 95% CI -0.5 to 4.2). Furthermore, no effect of tamoxifen on PRA (mean difference between withdrawal and continuation 0.03 +/- 0.5 ng/mL/h, 95% CI -0.3 to 0.2) or FENa (0.05 +/- 0.5, 95% CI -0.2 to 0.2) was detected. CONCLUSIONS: Tamoxifen seems to have no effect on BP, PRA, or FE(Na) in normotensive postmenopausal women.