This study will compare the bioavailabity of three new investigational combination formulations of Premarin and medroxyprogesterone acetate (MPA) with a currently marketed formulation of Premarin and MPA, Prempro™. Prempro™ is indicated for use after menopause in women with a uterus to reduce moderate to severe hot flashes; to treat moderate to severe dryness, itching, and burning, in and around the vagina; and to help reduce your chances of getting osteoporosis (thin weak bones). The purpose of this study is to determine if these new formulations of Premarin/MPA provide the same levels of estrogen and MPA in the blood as Prempro in healthy postmenopausal women.

Inclusion Criteria:

• Healthy, postmenopausal women ages 35 to 70 years, inclusive.
• Naturally postmenopausal women must not have had a menstrual period for at least six months, but less than 12 months, as confirmed by a blood test; or for at least 12 months with no blood hormone test confirmation. Naturally postmenopausal women must not have had a menstrual period since the age of 54. Surgically menopausal women must have undergone bilateral oophorectomy (removal of both ovaries) at least 6 months prior to the start of the study, and the surgical report may be requested to confirm the surgery date and that the surgery was not due to a cancerous condition.
• Nonsmoker or smoker of fewer than 10 cigarettes per day as determined by history. Must be able to abstain from smoking during the inpatient stay.