Generic Prometrium is a female hormone important for the regulation of ovulation and menstruation. Generic Prometrium is used to cause menstrual periods in women who have not yet reached menopause but are not having periods due to a lack of Generic Prometrium in the body. Generic Prometrium is also used to prevent overgrowth in the lining of the uterus in postmenopausal women who are receiving estrogen hormone replacement therapy. Generic Prometrium should not be used to prevent heart disease or dementia, because this medication may actually increase your risk of developing these conditions.