Context: Recommendations for postmenopausal hormone therapy have changed since the Women's Health Initiative indicated that estrogen was harmful for use in disease prevention; however, treatment of menopausal symptoms with low-dose estrogen remains an approved indication for use. Objective: To compare the short-term efficacy and adverse effects of 2 commonly used estrogens, conjugated equine estrogen (CEE) and 17β-estradiol, for reducing menopausal hot flashes by systematically reviewing randomized controlled trials. Data Sources: MEDLINE, EMBASE, the Cochrane Database of Systematic Reviews, and Cochrane Controlled Trials Registry were searched from the database start dates to July 2003 using database-specific key words. Reference lists of published articles, experts, and pharmaceutical manufacturers were also consulted. Study Selection: English-language abstracts of double-blind, randomized, placebo-controlled trials and systematic evidence reviews of oral CEE and oral and transdermal 17β-estradiol, and treatment of menopausal hot flashes and their adverse effects. Data Extraction: Study design, population characteristics, eligibility criteria, interventions, withdrawals, adverse effects, and results for each outcome. Study quality was assessed using predefined criteria based on parameters developed with the US Preventive Services Task Force and the UK National Health Services Centre. Data Synthesis: A total of 32 trials including 4 head-to-head comparisons met inclusion criteria; 14 trials met criteria for meta-analysis. All estrogen agents significantly reduced the weekly number of hot flashes compared with placebo (CEE, 1 trial: mean change, -19.1; 95% confidence interval [CI], -33.0 to -5.1; oral 17β-estradiol, 5 trials: pooled weighted mean difference, -16.8; 95% CI, -23.4 to -10.2; transdermal 17β-estradiol, 6 trials: pooled weighted mean difference, -22.4; 95% CI, -35.9 to -10.4); differences between agents were not significant. Breast tenderness and atypical vaginal bleeding were the most frequently reported adverse effects among estrogen users. The influence of progestin or progesterone use, cyclic and continuous regimens, and differences in adverse effects could not be determined. Conclusion: Conjugated equine estrogen and 17β-estradiol have consistent and comparable effects on treatment of menopausal hot flashes and may have similar short-term adverse effects.
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