Hormone Replacement Therapy with Conjugated Equine Estrogens and Medroxyprogesterone Acetate

Abstract

Of drug therapies currently in common use, perhaps none has been used longer and more extensively than conjugated equine estrogens (CEE). With yearly sales approaching one billion dollars on a global basis, these hormones (which now have been routinely combined with synthetic progestins for protection of the endometrium) continue to play an important and expanding role in the health and well-being of postreproductive women as we enter the 21st century. Although initially utilized alone, CEE therapy has adopted a changing face over the 50 years of its clinical use. Following revelations in the 1970s that CEE was capable of producing proliferation, hyperplasia, and perhaps even adenocarcinoma of the uterus, CEE was routinely combined with a progestational agent to prevent such endometrial change. The most popular of those regimens is CEE and medroxyprogesterone acetate (MPA). Given at varying doses from 2.5 to 10 mg per day, the combination of CEE and MPA now has a 20-year history of providing effective hormone replacement therapy (HRT) in postreproductive women. Recently, the concept of providing HRT as a continuous combined low-dose progestin therapy (as compared to a higher dose sequential regimen) has become extremely popular. The advantages of lower daily doses and the eventual development of amenorrhea in up to 80% of women utilizing this regimen make it a very practical long-term solution for HRT [1,2]. We will discuss a number of aspects of combined hormone replacement therapy in this paper.