Glossary · Treatments

Premarin (conjugated equine estrogens)

Also called: Conjugated equine estrogens, CEE.

Definition: Premarin is the original 1942 estrogen pill made from pregnant mare urine — a mixture of conjugated equine estrogens, not pure estradiol. Premarin works for menopausal symptoms and was the estrogen used in the WHI study. Most modern HRT now uses bioidentical estradiol, which more closely resembles what the body produced before menopause.

Detailed definition

Premarin (conjugated equine estrogens, CEE) was first marketed in 1942 by Wyeth (now Pfizer). It is extracted from the urine of pregnant mares and contains a complex mixture of estrogens — primarily estrone sulfate, equilin sulfate, 17α-dihydroequilin sulfate, and others — not pure human estradiol. Premarin was the dominant menopause estrogen in the United States for decades and was the estrogen used in both arms of the Women's Health Initiative. It is FDA-approved for vasomotor symptoms, GSM (vaginal cream form), and prevention of postmenopausal osteoporosis. Premarin is effective but is no longer first-line in most evidence-based menopause practices because bioidentical transdermal estradiol offers a more favorable VTE profile and replicates the molecule the body actually produced during the reproductive years.

Why it matters in menopause

Premarin still has a clinical role for women who tolerate it well and have been on it long-term, and Premarin Vaginal Cream is one of the FDA-approved low-dose vaginal estrogen options. For new starts, ClearedRx generally chooses bioidentical transdermal estradiol over CEE.

Sources

External references: Wikipedia.

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