Randomized comparison between orally and transdermally administered hormone replacement therapy regimens of long-term effects on 24-hour ambulatory blood pressure in postmenopausal women

Objective: The aim of this study was to assess whether oral delivery and transdermal delivery of sequential combined hormone replacement therapy have similar effects on systemic blood pressure, as measured by 24-hour automated ambulatory recordings. Study Design: Eighty-two healthy postmenopausal women, of whom 73 completed the study, were randomly assigned to start hormone replacement therapy with either orally (n = 38) or transdermally (n = 35) administered medication. Ambulatory blood pressure was recorded for a 24-hour period before the start of hormone replacement therapy and again 2 and 6 months later. Analysis of variance was used for data analysis. Results: Hormone replacement therapy by both oral and transdermal routes was associated with slight but nonsignificant drops in mean 24-hour systolic and diastolic ambulatory blood pressure. Daytime systolic ambulatory blood pressure (mean ± SE) fell significantly (P< .05) and similarly at 2 months in the oral (3.8 ± 0.2 mm Hg) and transdermal (4.0 ± 0.3 mm Hg) treatment groups. The daytime ambulatory blood pressure remained significantly lower than baseline at 6 months in the oral treatment group (–3.6 ± 0.3 mm Hg), whereas the fall at 6 months in the transdermal group (–3.1 ± 0.3 mm Hg) was not significant. Mean daytime diastolic ambulatory blood pressure was reduced in both the oral (–1.8 ± 0.8 mm Hg) and transdermal (–3.5 ± 0.7 mm Hg; P< .05) treatment groups at 2 months but not at 6 months. Nighttime ambulatory blood pressures in both groups remained unaffected by hormone replacement therapy. Conclusion: Sequential combined hormone replacement therapy delivered by both oral and transdermal routes caused significant falls in the daytime ambulatory blood pressure of normotensive postmenopausal women at 2 months of treatment. This fall persisted as long as 6 months of treatment in the oral treatment group but not in the transdermal treatment group. (Am J Obstet Gynecol 2001;184:904-9.)