Pharmacology Update

Estradiol Transdermal System (Menostar)

By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD

The FDA has approved a low dose estradiol transdermal patch for prevention of osteoporosis in menopausal women. Menostar provides the lowest dose of estrogen of any product on the market, so low in fact that concomitant progestins are only required once or twice per year for women with an intact uterus. This estradiol transdermal system is manufactured by 3M Pharmaceuticals and marketed by Berlex.


The estradiol transdermal system is indicated for the prevention of postmenopausal osteoporosis.1


The transdermal system should be applied to a clean, dry area of the lower abdomen once weekly. The site should be rotated with an interval of at least 1 week. It is recommended that women with an intact uterus be treated also with a progestin for 14 days every 6-12 months and undergo an endometrial biopsy yearly or as clinical indicated.1

The transdermal system releases 14 mcg of 17-estradiol per day.

Potential Advantages

Menostar delivers the lowest dose (14 mcg) estrogen currently available with the next lowest dose being 25 mcg daily. Menostar has been shown to produce an increase in bone mineral density (BMD) of 3% above baseline at the lumbar spine and 0.84% above baseline at the hip after 2 years of treatment.1

Potential Disadvantages

Menostar is not indicated for the treatment of postmenopausal symptoms and there are no data regarding fracture prevention. Even with this low dose of estrogen, progestin therapy is still recommended in patient with intact uterus albeit less often.


Menostar is the latest estrogen formulation to be approved at a time when estrogen therapy has come under increased scrutiny. It is approved only for the prevention of osteoporosis. The efficacy and safety was assessed in a 2-year, randomized, placebo-controlled, multicenter study in 417 postmenopausal women ages 60 to 80. BMD was increased by 3% above baseline at the lumbar spine compared to 0.4% for placebo. At the hip the increase was 0.84% vs -0.71% respectively.1 Application site reactions were reported to be 9%.

Menostar is more expensive then the previous low dose estradiol patches. Its average wholesale cost is $49.50 for 4 patches (one month) compared to $33.91-$38.13 for Climara, Alora, or Esclim.

Clinical Indications

Since the findings of the Women’s Health Initiative (WHI) and the Women’s Health Initiative Memory Study (WHIMS) estrogen have fallen out of favor in general and specifically for preventing osteoporosis. Bisphosphonates are now the preferred therapy for both preventing and treating osteoporosis. The American College of Obstetrics and Gynecology does not recommend hormonal treatment solely for the prevention of osteoporosis.2 Hormonal treatment may be appropriate, however, for the control of postmenopausal symptoms. It is not known whether Menostar is effective in managing these symptoms and it is not FDA approved for this indication.


1. Menostar Product Information. Berlex. June 2004.