GENERIC NAME: conjugated equine estrogens and medroxyprogesterone acetate
BRAND NAME: Prempro, Premphase
DRUG CLASS AND MECHANISM: Prempro and Premphase are combinations of conjugated estrogens (Premarin) and medroxyprogesterone (Provera). Estrogens and progestins are the two major classes of female hormones. Conjugated estrogens are a mixture of several different estrogens (estrogen salts) that are derived from natural sources and blended to approximate the composition of estrogens in the urine of pregnant horses. The main components are sodium estrone sulphate and sodium equilin sulfate. Estrogens have widespread effects on many tissues in the body. Estrogens cause growth and development of the female sexual organs and maintain female sexual characteristics such as the growth of underarm and pubic hair, body contours, and skeleton. Estrogens also increase secretions from the cervix and growth of the inner lining of the uterus (endometrium). Medroxyprogesterone is a derivative of progesterone, a naturally occurring female progestin. Progestins are responsible for changes in the mucus and inner lining of the uterus (endometrium) during the second half (secretory phase) of the menstrual cycle. Progestins prepare the endometrium for implantation of the embryo. Once an embryo implants in the endometrium, for example, and pregnancy occurs, progestins help maintain the pregnancy. At high doses, progestins can prevent ovulation (release of the egg from the ovary) and thereby prevent pregnancy. The FDA approved Prempro and Premphase in June 2003.
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