Promestriene (3-propyl ethyl, 17B-methyl estradiol) is a synthetic estrogen analog that has been reported to significantly improve the symptoms of vaginal atrophy caused by estrogen deprivation in topical application. Promestriene (3-propyl ethyl, 17B-methyl estradiol) is a synthetic estrogen analog that has been reported to significantly improve the symptoms of vaginal atrophy caused by estrogen deprivation in topical application.