conjugated equine estrogens and medroxyprogesterone acetate, Prempro, Premphase

  • Pharmacy Author:
    Omudhome Ogbru, PharmD

    Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

  • Medical Editor: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

What is conjugated equine estrogens and medroxyprogesteron, and how does it work (mechanism of action)?

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.

What brand names are available for conjugated equine estrogens and medroxyprogesteron?

Prempro, Premphase

Is conjugated equine estrogens and medroxyprogesteron available as a generic drug?

GENERIC AVAILABLE: No

Do I need a prescription for conjugated equine estrogens and medroxyprogesteron?

Yes

What are the side effects of conjugated equine estrogens and medroxyprogesteron?

The most common side effects of Prempro and Premphase are:

Other important side effects include:

  • Headaches,
  • breakthrough bleeding, and
  • spotting.

The Women's Health Initiative found that postmenopausal women (50-79 years old) taking conjugated estrogens, 0.625 mg daily, in combination with medroxyprogesterone, 2.5 mg daily, for five years, had an increased risk of heart attacks, stroke, breast cancer, and blood clots, while postmenopausal women taking conjugated estrogens without progesterone experienced only increased strokes but not increased blood clots, heart disease, or breast cancer. There was an increased risk of impaired cognition and/or dementia among women over age 65 treated with either estrogens or estrogens and medroxyprogesterone.

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