The Menostar transdermal system provides systemic estrogen therapy by releasing 17b-estradiol, the major estrogenic hormone secreted by the human ovary.

Endogenous estrogens are largely responsible for the development and maintenance of the female reproductive system and secondary sexual characteristics. Although circulating estrogens exist in a dynamic equilibrium of metabolic interconversions, estradiol is the principal intracellular human estrogen and is substantially more potent than its metabolites, estrone and estriol, at the receptor level.

The primary source of estrogen in normally cycling adult women is the ovarian follicle, which secretes 70 to 500 mcg of estradiol daily, depending on the phase of the menstrual cycle. After menopause, most endogenous estrogen is produced by conversion of androstenedione, secreted by the adrenal cortex, to estrone by peripheral tissues. Thus, estrone and the sulfate conjugated form, estrone sulfate, are the most abundant circulating estrogens in postmenopausal women.

Estrogens act through binding to nuclear receptors in estrogen-responsive tissues. To date, two estrogen receptors have been identified. These vary in proportion from tissue to tissue.

Circulating estrogens modulate the pituitary secretion of the gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH), through a negative feedback mechanism. Estrogens act to reduce the elevated levels of these hormones seen in postmenopausal women.

The decline of ovarian estrogen production that accompanies menopause or oophorectomy results in the acceleration of bone loss and bone resorption. Bone resorption is increased more than bone formation especially in the early years of menopause where bone loss is the greatest. In some women, these changes will eventually lead to decreased bone mass, osteoporosis and increased risk for fractures, particularly that of the spine, hip, and wrist. Vertebral fractures are the most common type of osteoporotic fracture in postmenopausal women.

Postmenopausal women with low serum estradiol concentrations and high serum concentrations of sex hormone binding globulin (SHBG) have an increased risk of hip and vertebral fractures.

Postmenopausal estrogen therapy decreases bone resorption, helping to reestablish balance between resorption and formation. This effect appears to be effective for as long as treatment is continued.

The bioavailability of estradiol following application of a Menostar transdermal system, relative to that of a transdermal system delivering 25 mcg/day, was investigated in 18 healthy postmenopausal women mean age 66 years (range 60-80 years). The mean serum estradiol concentrations upon administration of the two patches to the lower abdomen are shown in Figure 1. Transdermal administration of Menostar produced geometric mean serum concentration (Cavg) of estradiol of 13.7 pg/mL. No patches failed to adhere during the one week application period of both transdermal systems. Following application of the Menostar transdermal system to the abdomen, it is estimated to provide an average nominal in-vivo daily delivery of 14 mcg estradiol/day.

Bookmark this page: