Effect of estrogen receptor modulator tamoxifen on blood pressure, plasma renin activity, and renal sodium excretion

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 (FENa) 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 FENa in normotensive postmenopausal women.