DIVIGEL — estradiol gel
Physicians Total Care, Inc.
Close clinical surveillance of all women taking estrogens is important. Adequate diagnostic measures, including endometrial sampling when indicated, should be undertaken to rule out malignancy in all cases of undiagnosed persistent or recurring abnormal vaginal bleeding. There is no evidence that the use of “natural” estrogens results in a different endometrial risk profile than synthetic estrogens at equivalent estrogen doses. (See WARNINGS, Malignant neoplasms, Endometrial cancer.)
The estrogen-alone substudy of the Women’s Health Initiative (WHI) reported increased risks of stroke and deep vein thrombosis in postmenopausal women (50 to 79 years of age) during 6.8 years and 7.1 years, respectively, of treatment with oral conjugated estrogens (CE 0.625 mg) alone per day, relative to placebo. (See CLINICAL STUDIES and WARNINGS, Cardiovascular disorders.)
The estrogen-plus-progestin substudy of the WHI reported increased risk of myocardial infarction, stroke, invasive breast cancer, pulmonary emboli, and deep vein thrombosis in postmenopausal women (50 to 79 years of age) during 5.6 years of treatment with oral conjugated estrogens (CE 0.625 mg) combined with medroxyprogesterone acetate (MPA 2.5 mg) per day, relative to placebo. (See CLINICAL STUDIES and WARNINGS, Cardiovascular disorders and Malignant neoplasms, Breast cancer.)
The Women’s Health Initiative Memory Study (WHIMS), a substudy of the WHI, reported an increased risk of developing probable dementia in postmenopausal women 65 years of age or older during 5.2 years of treatment with CE 0.625 mg alone and during 4 years of treatment with CE 0.625 mg combined with MPA 2.5 mg, relative to placebo. It is unknown whether this finding applies to younger postmenopausal women. (See CLINICAL STUDIES, WARNINGS, Dementia, and PRECAUTIONS, Geriatric Use.)
Other doses of oral conjugated estrogens with medroxyprogesterone acetate, and other combinations and dosage forms of estrogens and progestins were not studied in the WHI clinical trials and, in the absence of comparable data, these risks should be assumed to be similar. Because of these risks, estrogens with or without progestins should be prescribed at the lowest effective doses and for the shortest duration consistent with treatment goals and risks for the individual woman.
Divigel® (estradiol gel) 0.1% is a clear, colorless gel, which is odorless when dry. It is designed to deliver sustained circulating concentrations of estradiol when applied once daily to the skin. The gel is applied to a small area (200 cm2) of the thigh in a thin, quick-drying layer. Divigel® is available in three doses of 0.25, 0.5, and 1.0 g for topical application (corresponding to 0.25, 0.5, and 1.0 mg estradiol, respectively).
The active component of the topical gel is estradiol.
Estradiol is a white crystalline powder, chemically described as estra-1,3,5(10)-triene-3,17β-diol. It has an empirical formula of C18 H24 O2 and molecular weight of 272.39. The structural formula is:
The remaining components of the gel (carbomer, ethanol, propylene glycol, purified water, and triethanolamine) are pharmacologically inactive.
Divigel® provides estrogen therapy by delivering estradiol, the major estrogenic hormone secreted by the human ovary, to the systemic circulation following topical application.
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.
Estradiol diffuses across intact skin and into the systemic circulation by a passive absorption process, with diffusion across the stratum corneum being the rate-limiting factor.
In a 14-day, Phase 1, multiple-dose study, Divigel® demonstrated linear and approximately dose-proportional estradiol pharmacokinetics at steady state for both AUC0-24 and Cmax following once daily dosing to the skin of either the right or left upper thigh (Table 1).
* Median (Min, Max).
|Parameter (units)||Divigel ® 0.25 g||Divigel ® 0.5 g||Divigel ® 1.0 g|
|AUC0-24 (pg•h/mL)||236 (94)||504 (149)||732 (81)|
|Cmax (pg/mL)||14.7 (84)||28.4 (139)||51.5 (86)|
|Cavg (pg/mL)||9.8 (92)||21 (148)||30.5 (81)|
|tmax * (h)||16 (0, 72)||10 (0, 72)||8 (0, 48)|
Steady-state serum concentration of estradiol are achieved by day 12 following daily application of Divigel® to the skin of the upper thigh. The mean (SD) serum estradiol levels following once daily dosing at day 14 are shown in Figure 1.
Figure 1: Mean (SD) Serum Estradiol Concentrations (Values Uncorrected for Baseline) on Day 14 Following Multiple Daily Doses of Divigel 0.1%
The effect of sunscreens and other topical lotions on the systemic exposure of Divigel® has not been evaluated. Studies conducted using topical estrogen gel approved products have shown that sunscreens have the potential for changing the systemic exposure of topically applied estrogen gels.
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