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PRESCRIBING INFORMATION Estradiol Transdermal System Continuous Delivery (Once-Weekly), USP
Table 1 provides a summary of estradiol pharmacokinetic parameters determined during evaluation of Estradiol Transdermal System Continuous Delivery (Once-Weekly).
| Estradiol Delivery Rate | Surface Area (cm2 ) | Application Site | No. of Subjects | Dosing | Cmax (pg/mL) | Cmin (pg/mL) | Cavg (pg/mL) |
| 0.025 | 7.75 | Abdomen | 24 | Single | 32 | 17 | 22 |
| 0.05 | 15.5 | Abdomen | 102 | Single | 71 | 29 | 41 |
| 0.1 | 31 | Abdomen | 139 | Single | 147 | 60 | 87 |
| 0.1 | 31 | Buttock | 38 | Single | 174 | 71 | 106 |
The relative standard deviation of each pharmacokinetic parameter after application to the abdomen averaged 50%, which is indicative of the considerable intersubject variability associated with transdermal drug delivery. The relative standard deviation of each pharmacokinetic parameter after application to the buttock was lower than that after application to the abdomen (e.g., for Cmax 39% vs. 62%, and for Cavg 35% vs. 48%).
DistributionThe distribution of exogenous estrogens is similar to that of endogenous estrogens.
Estrogens are widely distributed in the body and are generally found in higher concentrations in the sex hormone target organs. Estrogens circulate in the blood largely bound to sex hormone binding globulin (SHBG) and albumin.
MetabolismExogenous estrogens are metabolized in the same manner as endogenous estrogens. Circulating estrogens exist in a dynamic equilibrium of metabolic interconversions. These transformations take place mainly in the liver. Estradiol is converted reversibly to estrone, and both can be converted to estriol, which is the major urinary metabolite. Estrogens also undergo enterohepatic recirculation via sulfate and glucuronide conjugation in the liver, biliary secretion of conjugates into the intestine, and hydrolysis in the gut followed by reabsorption. In postmenopausal women, a significant proportion of the circulating estrogens exist as sulfate conjugates, especially estrone sulfate, which serves as a circulating reservoir for the formation of more active estrogens.
ExcretionEstradiol, estrone and estriol are excreted in the urine along with glucuronide and sulfate conjugates.
Special PopulationsGeriatricThere have not been sufficient numbers of geriatric patients involved in clinical studies utilizing Estradiol Transdermal System Continuous Delivery (Once-Weekly) to determine whether those over 65 years of age differ from younger subjects in their response to Estradiol Transdermal System Continuous Delivery (Once-Weekly).
PediatricNo pharmacokinetic study for Estradiol Transdermal System Continuous Delivery (Once-Weekly) has been conducted in a pediatric population.
GenderEstradiol Transdermal System Continuous Delivery (Once-Weekly) is indicated for use in women only.
RaceNo studies were done to determine the effect of race on the pharmacokinetics of Estradiol Transdermal System Continuous Delivery (Once-Weekly).
Patients with Renal ImpairmentTotal estradiol serum levels are higher in postmenopausal women with end stage renal disease (ESRD) receiving maintenance hemodialysis than in normal subjects at baseline and following oral doses of estradiol. Therefore, conventional transdermal estradiol doses used in individuals with normal renal function may be excessive for postmenopausal women with ESRD receiving maintenance hemodialysis.
Patients with Hepatic ImpairmentEstrogens may be poorly metabolized in patients with impaired liver function and should be administered with caution.
Drug InteractionsIn vitro and in vivo studies have shown that estrogens are metabolized partially by cytochrome P450 3A4 (CYP3A4). Therefore, inducers or inhibitors of CYP3A4 may affect estrogen drug metabolism. Inducers of CYP3A4 such as St. John’s Wort preparations (Hypericum perforatum), phenobarbital, carbamazepine, and rifampin may reduce plasma concentrations of estrogens, possibly resulting in a decrease in therapeutic effects and/or changes in the uterine bleeding profile. Inhibitors of CYP3A4 such as erythromycin, clarithromycin, ketoconazole, itraconazole, ritonavir and grapefruit juice may increase plasma concentrations of estrogens and may result in side effects.
AdhesionAn open-label study of adhesion potentials of placebo transdermal systems that correspond to the 7.75 cm2 and 15.5 cm2 sizes of Estradiol Transdermal System Continuous Delivery (Once-Weekly) was conducted in 112 healthy women of 45 to 75 years of age. Each woman applied both transdermal systems weekly, on the upper outer abdomen, for 3 consecutive weeks. It should be noted that lower abdomen and upper quadrant of the buttock are the approved sites of application for Estradiol Transdermal System Continuous Delivery (Once-Weekly).
The adhesion assessment was done visually on Days 2, 4, 5, 6, 7 of each week of transdermal system wear. A total of 1,654 adhesion observations were conducted for 333 transdermal systems of each size.
Of these observations, approximately 90% showed essentially no lift for both the 7.75 cm2 and 15.5 cm2 transdermal systems. Of the total number of transdermal systems applied, approximately 5% showed complete detachment for each size. Adhesion potentials of the 23.25 cm2 and 31 cm2 sizes of transdermal systems (0.075 mg/day and 0.1 mg/day) have not been studied.
Clinical StudiesEffects on vasomotor symptomsA study of 214 women 25 to 74 years old met the qualification criteria and were randomly assigned to one of the three treatment groups: 72 to the 0.05 mg estradiol patch, 70 to the 0.1 mg estradiol patch, and 72 to placebo. Potential subjects were postmenopausal women in good general health who experienced vasomotor symptoms. Natural menopause patients had not menstruated for at least 12 months and surgical menopause patients had undergone bilateral oophorectomy at least 4 weeks before evaluation for study entry. In order to enter the 11 week treatment phase of the study, potential subjects must have experienced a minimum of five moderate to severe hot flushes per week, or a minimum of 15 hot flushes of any severity per week, for 2 consecutive weeks. Women wore the patches in a cyclical fashion (three weeks on and one week off).
During treatment, all subjects used diaries to record the number and severity of hot flushes. Subjects were monitored by clinic visits at the end of weeks 1, 3, 7, and 11 and by telephone at the end of weeks 4, 5, 8, and 9.
Adequate data for the analysis of efficacy was available from 191 subjects. The results are presented as the mean ± SD number of flushes in each of the 3 treatment weeks of each 4 week cycle. In the 0.05 mg estradiol group, the mean weekly hot flush rate across all treatment cycles decreased from 46 ± 6.5 at baseline to 20 ± 3.0 (-67.0%). The 0.1 mg estradiol group had a decline in the mean weekly hot flush rate from 52 ± 4.4 at baseline to 16 ± 2.4 (-72.0%). In the placebo group, the mean weekly hot flush rate declined from 53 ± 4.5 at baseline to 46 ± 6.5 (-18.1%). Compared with placebo, the 0.05 mg and 0.1 mg estradiol groups showed a statistically significantly larger mean decrease in hot flushes across all treatment cycles (P less than 0.05). When the response to treatment was analyzed for each of the three cycles of therapy, similar statistically significant differences were observed between both estradiol treatment groups and the placebo group during all treatment cycles.
In a double-blind, placebo-controlled, randomized study of 187 women receiving Estradiol Transdermal System Continuous Delivery (Once-Weekly) 0.025 mg/day or placebo continuously for up to three 28 day cycles, the Estradiol Transdermal System Continuous Delivery (Once-Weekly) 0.025 mg/day dosage was shown to be statistically better than placebo at weeks 4 and 12 for relief of both the frequency and severity of moderate to severe vasomotor symptoms.
| Treatment Group | Statistics | Week 4 | Week 8 | Week 12 |
| E2 TDS | N | 82 | 84 | 68 |
| Mean | -6.45 | -7.69 | -7.56 | |
| SD | 4.65 | 4.76 | 4.64 | |
| Placebo | N | 83 | 71 | 65 |
| Mean | -5.11 | -5.98 | -5.98 | |
| SD | 7.43 | 8.63 | 9.69 | |
| p-Value | Less than 0.002 | Less than 0.003 |
A second active-control trial of 193 randomized subjects was supportive of the placebo-controlled trial.
Effects on bone mineral densityA two year clinical trial enrolled a total of 175 healthy, hysterectomized, postmenopausal, non-osteoporotic (i.e., lumbar spine bone mineral density less than 0.9 gm/cm2) women at 10 study centers in the United States. One hundred twenty nine subjects were allocated to receive active treatment with four different doses of estradiol patches (7.75 cm2, 15.5 cm2, 23.25 cm2, 31 cm2) and 46 subjects were allocated to receive placebo patches. Seventy seven percent of the randomized subjects (100 on active drug and 34 on placebo) contributed data to the analysis of percent change of A-P spine bone mineral density (BMD), the primary efficacy variable (see Figure 3). A statistically significant overall treatment effect at each timepoint was noted, implying bone preservation for all active treatment groups at all timepoints, as opposed to bone loss for placebo at all timepoints.
Figure 3 Mean Percent Change from Baseline in Lumbar Spine (A-P View) Bone Mineral Density by Treatment and Time Last Observation Carried Forward
Percent change in BMD of the total hip (see Figure 4), was also statistically significantly different from placebo for all active treatment groups. The results of the measurements of biochemical markers supported the finding of efficacy for all doses of transdermal estradiol. Serum osteocalcin levels decreased, indicative of a decrease in bone formation, at all timepoints for all active treatment doses, statistically significantly different from placebo (which generally rose). Urinary deoxypyridinoline and pyridinoline changes also suggested a decrease in bone turnover for all active treatment groups.
Figure 4 Mean Percent Change from Baseline in Total Hip by Treatment and Time Last Observation Carried Forward
Footnote: This figure is based on 74% of the randomized subjects (95 on active drug and 34 on placebo).
Women's Health Initiative StudiesThe Women’s Health Initiative (WHI) enrolled a total of 27,000 predominantly healthy postmenopausal women to assess the risks and benefits of either the use of oral 0.625 mg conjugated estrogens (CE) per day alone or the use of 0.625 mg conjugated estrogens plus 2.5 mg medroxyprogesterone acetate (MPA) per day compared to placebo in the prevention of certain chronic diseases. The primary endpoint was the incidence of coronary heart disease (CHD) (nonfatal myocardial infarction and CHD death), with invasive breast cancer as the primary adverse outcome studied. A “global index” included the earliest occurrence of CHD, invasive breast cancer, stroke, pulmonary embolism (PE), endometrial cancer, colorectal cancer, hip fracture, or death due to other cause. The study did not evaluate the effects of CE or CE/MPA on menopausal symptoms.
The CE/MPA substudy was stopped early because, according to the predefined stopping rule, the increased risk of breast cancer and cardiovascular events exceeded the specified benefits included in the “global index.” Results of the CE/MPA substudy, which included 16,608 women (average age of 63 years, range 50 to 79; 83.9% White, 6.5% Black, 5.5% Hispanic), after an average follow-up of 5.2 years are presented in Table 3 below:
| Event | Relative Risk CE/MPA vs. Placebo at 5.2 Years (95% CI (*,1) | Placebo N=8102 Absolute Risk per | CE/MPA N=8506 10,000 Person-years |
| CHD events Nonfatal MI CHD death | 1.29 (1.02-1.63) 1.32 (1.02-1.72) 1.18 (0.70-1.97) | 30 23 6 | 37 30 7 |
| Invasive breast cancer (2) | 1.26 (1.00-1.59) | 30 | 38 |
| Stroke | 1.41 (1.07-1.85) | 21 | 29 |
| Pulmonary embolism | 2.13 (1.39-3.25) | 8 | 16 |
| Colorectal cancer | 0.63 (0.43-0.92) | 16 | 10 |
| Endometrial cancer | 0.83 (0.47-1.47) | 6 | 5 |
| Hip fracture | 0.66 (0.45-0.98) | 15 | 10 |
| Death due to cause others than the events above | 0.92 (0.74-1.14) | 40 | 37 |
| Global Index (3) | 1.15 (1.03-1.28) | 151 | 170 |
| Deep vein thrombosis (4) | 2.07 (1.49-2.87) | 13 | 26 |
| Vertebral fractures (4) | 0.66 (0.44-0.98) | 15 | 9 |
| Other osteoporotic fractures (4) | 0.77 (0.69-0.86) | 170 | 131 |
(*) adapted from JAMA, 2002; 288:321-333
(1) * nominal confidence intervals unadjusted from multiple looks and multiple comparisons
(2) includes metastatic and non-metastatic breast cancer with the exceptioin of in situ breast cancer
(3) a subset of the events was combined in a "global index", defined as the earliest occurrence of CHD events,
invasive breast cancer, stroke, pulmonary embolism, endometrial cancer, colorectal cancer, hip fracture,
or death due to other causes
(4) not included in Global Index
For those outcomes included in the “global index,” absolute excess risks per 10,000 women-years in the group treated with CE/MPA were 7 more CHD events, 8 more strokes, 8 more PEs, and 8 more invasive breast cancers, while absolute risk reductions per l0,000 women-years were 6 fewer colorectal cancers and 5 fewer hip fractures. The absolute excess risk of events included in the “global index” was 19 per 10,000 women-years. There was no difference between the groups in terms of all-cause mortality. (See BOXED WARNINGS , WARNINGS, and PRECAUTIONS.)
Women's Health Initiative Memory StudyThe Women’s Health Initiative Memory Study (WHIMS), a substudy of WHI, enrolled 4,532 predominantly postmenopausal women 65 years of age and older (47% were age 65 to 69 years, 35% were 70 to 74 years, and 18% were 75 years of age and older) to evaluate the effects of CE/MPA (0.625 mg conjugated estrogens plus 2.5 mg medroxyprogesterone acetate) on the incidence of probable dementia (primary outcome) compared with placebo. After an average follow-up of 4 years, 40 women in the estrogen/progestin group (45 per 10,000 women-years) and 21 in the placebo group (22 per 10,000 women-years) were diagnosed with probable dementia. The relative risk of probable dementia in the hormone therapy group was 2.05 (95% CI, 1.21 to 3.48) compared to placebo. Differences between groups became apparent in the first year of treatment. It is unknown whether these findings apply to younger postmenopausal women. (See BOXED WARNINGS and WARNINGS, Dementia and PRECAUTIONS, Geriatric Use.)