Get your patient on Norethindrone Acetate And Ethinyl Estradiol - Norethindrone Acetate And Ethinyl Estradiol tablet (Norethindrone Acetate And Ethinyl Estradiol)

Limitation of Use

When prescribing solely for the prevention of postmenopausal osteoporosis, first consider the use of non-estrogen medications. Consider estrogen therapy only for women at significant risk of osteoporosis.

Take a single norethindrone acetate and ethinyl estradiol tablet, orally once daily.

Take a single norethindrone acetate and ethinyl estradiol tablet, orally once daily

Risk Summary

Norethindrone acetate and ethinyl estradiol tablets are not indicated for use in pregnancy. There are no data with the use of norethindrone acetate and ethinyl estradiol tablets in pregnant women; however, epidemiologic studies and meta-analyses have not found an increased risk of genital or nongenital birth defects (including cardiac anomalies and limb-reduction defects) following exposure to combined (estrogens and progestins) product before conception or during early pregnancy.

In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

Risk Summary

Estrogens plus progestogens are present in human milk and can reduce milk production in breast-feeding women. This reduction can occur at any time but is less likely to occur once breast-feeding is well-established. The development and health benefits of breastfeeding should be considered along with the mother’s clinical need for norethindrone acetate and ethinyl estradiol tablets and any potential adverse effects on the breastfed child from norethindrone acetate and ethinyl estradiol tablets or from the underlying maternal condition.

Norethindrone acetate and ethinyl estradiol tablets are not indicated for use in pediatric patients. Clinical studies have not been conducted in the pediatric population.

There have not been sufficient numbers of geriatric women involved in clinical studies utilizing norethindrone acetate and ethinyl estradiol tablets to determine whether those over 65 years of age differ from younger subjects in their response to norethindrone acetate and ethinyl estradiol tablets.

The Women’s Health Initiative Studies

In the WHI estrogen plus progestin substudy (daily CE [0.625 mg] plus MPA [2.5 mg] versus placebo), there was a higher relative risk of nonfatal stroke and invasive breast cancer in women greater than 65 years of age [see Clinical Studies (14.5 )] .

In the WHI estrogen-alone substudy (daily CE [0.625 mg]-alone versus placebo), there was a higher relative risk of stroke in women greater than 65 years of age [see Clinical Studies (14.5 )] .

The Women’s Health Initiative Memory Study

In the WHIMS ancillary studies of postmenopausal women 65 to 79 years of age, there was an increased risk of developing probable dementia in women receiving estrogen plus progestin or estrogen-alone when compared to placebo [see Warnings and Precautions (5.3 ), and Clinical Studies (14.6 )] .

Since both ancillary studies were conducted in women 65 to 79 years of age, it is unknown whether these findings apply to younger postmenopausal women8 [see Warnings and Precautions (5.3 ), and Clinical Studies (14.6 )] .

Increased risk of PE, DVT, stroke, and MI are reported with estrogen plus progestin therapy. Increased risks of stroke and DVT are reported with estrogen-alone therapy. Immediately discontinue estrogen with or without progestogen therapy if any of these occur or are suspected.

Manage appropriately any risk factors for arterial vascular disease (for example, hypertension, diabetes mellitus, tobacco use, hypercholesterolemia, and obesity) and/or venous thromboembolism (VTE) (for example, personal history or family history of VTE, obesity, and systemic lupus erythematosus).

Stroke

The WHI estrogen plus progestin substudy reported a statistically significant increased risk of stroke in women 50 to 79 years of age receiving daily CE (0.625 mg) plus MPA (2.5 mg) compared to women in the same age group receiving placebo (33 versus 25 strokes per 10,000 women- years) [ see Clinical Studies (14.5 ) ]. The increase in risk was demonstrated after the first year and persisted. ¹ Immediately discontinue estrogen with or without progestogen therapy if a stroke occurs or is suspected.

The WHI estrogen-alone substudy, reported a statistically significant increased risk of stroke in women 50 to 79 years of age receiving daily conjugated estrogens CE (0.625 mg)-alone compared to women in the same age group receiving placebo (45 versus 33 per 10,000 women-years). The increase in risk was demonstrated in year 1 and persisted [see Clinical Studies (14.5 ) ] . Immediately discontinue estrogen-alone therapy if a stroke occurs or is suspected.

Subgroup analyses of women 50 to 59 years of age suggest no increased risk of stroke for those women receiving CE (0.625 mg)-alone versus those receiving placebo (18 versus 21 per 10,000 women-years). ¹

Coronary Heart Disease

The WHI estrogen plus progestin substudy reported an increased risk (not statistically significant) of coronary heart disease (CHD) events (defined as nonfatal MI, silent MI, or CHD death) in those women receiving daily CE (0.625 mg) plus MPA (2.5 mg) compared to women receiving placebo (41 versus 34 per 10,000 women-years). ¹ An increase in relative risk was demonstrated in year 1, and a trend toward decreasing relative risk was reported in years 2 through 5 [see Clinical Studies (14.5 ) ] .

The WHI estrogen-alone substudy reported no overall effect on CHD events in women receiving estrogen-alone compared to placebo ² [see Clinical Studies (14.5 )] .

Subgroup analyses of women 50 to 59 years of age, who were less than 10 years since menopause, suggest a reduction (not statistically significant) of CHD events in those women receiving CE (0.625 mg)-alone compared to placebo (8 versus 16 per 10,000 woman-years). ¹

In postmenopausal women with documented heart disease (n = 2,763), average 66.7 years of age, in a controlled clinical trial of secondary prevention of cardiovascular disease (Heart and Estrogen/Progestin Replacement Study [HERS]), treatment with daily CE (0.625 mg) plus MPA (2.5 mg) demonstrated no cardiovascular benefit. During an average follow-up of 4.1 years, treatment with CE plus MPA did not reduce the overall rate of CHD events in postmenopausal women with established CHD. There were more CHD events in the CE plus MPA-treated group than in the placebo group in year 1, but not during the subsequent years. Two thousand, three hundred and twenty-one (2,321) women from the original HERS trial agreed to participate in an open label extension of HERS, HERS II. Average follow-up in HERS II was an additional 2.7 years, for a total of 6.8 years overall. Rates of CHD events were comparable among women in the CE plus MPA group and the placebo group in HERS, HERS II, and overall.

Venous Thromboembolism

The WHI estrogen plus progestin substudy reported a statistically significant 2-fold greater rate of VTE (DVT and PE) in women receiving daily CE (0.625 mg) plus MPA (2.5 mg) compared to women receiving placebo (35 versus 17 per 10,000 women-years). Statistically significant increases in risk for both DVT (26 versus 13 per 10,000 women-years) and PE (18 versus 8 per 10,000 women-years) were also demonstrated. The increase in VTE risk was demonstrated during the first year and persisted ³ [see Clinical Studies (14.5 )] . Immediately discontinue estrogen plus progestogen therapy if a VTE occurs or is suspected.

In the WHI estrogen-alone substudy, the risk of VTE was increased for women receiving daily CE (0.625 mg)-alone compared to placebo (30 versus 22 per 10,000 women-years), although only the increased risk of DVT reached statistical significance (23 versus 15 per 10,000 women-years). The increase in VTE risk was demonstrated during the first 2 years ⁴ [see Clinical Studies (14.5 )] . Immediately discontinue estrogen-alone therapy if a VTE occurs or is suspected.

If feasible, discontinue estrogens at least 4 to 6 weeks before surgery of the type associated with an increased risk of thromboembolism or during periods of prolonged immobilization.

Breast Cancer

After a mean follow-up of 5.6 years, the WHI substudy of daily CE (0.625 mg) plus MPA (2.5 mg) reported an increased risk of invasive breast cancer in women who took daily CE plus MPA compared to placebo. In this substudy, prior use of estrogen-alone or estrogen plus progestin therapy was reported by 26 percent of the women. The relative risk of invasive breast cancer was 1.24, and the absolute risk was 41 versus 33 cases per 10,000 women-years for CE plus MPA compared with placebo [see Clinical Studies (14.5 )] . Among women who reported prior use of hormone therapy, the relative risk of invasive breast cancer was 1.86 and the absolute risk was 46 versus 25 cases per 10,000 women-years for CE plus MPA compared with placebo. Among women who reported no prior use of hormone therapy, the relative risk of invasive breast cancer was 1.09, and the absolute risk was 40 versus 36 cases per 10,000 women-years for CE plus MPA compared with placebo. In the same substudy, invasive breast cancers were larger, were more likely to be node positive, and were diagnosed at a more advanced stage in the CE (0.625 mg) plus MPA (2.5 mg) group compared with the placebo group. Metastatic disease was rare with no apparent difference between the two groups. Other prognostic factors, such as histologic subtype, grade and hormone receptor status did not differ between the groups ⁵ [see Clinical Studies (14.5 )].

The WHI substudy of daily CE (0.625 mg)-alone provided information about breast cancer in estrogen-alone users. In the WHI estrogen-alone substudy, after an average follow up of 7.1 years, daily CE-alone was not associated with an increased risk of invasive breast cancer (relative risk [RR] 0.80 compared to placebo ⁶ [see Clinical Studies (14.5 )] .

Consistent with the WHI clinical trials, observational studies have also reported an increased risk of breast cancer for estrogen plus progestin therapy, and a smaller increased risk for estrogen-alone therapy, after several years of use. One large meta-analysis of prospective cohort studies reported increased risks that were dependent upon duration of use and could last up to >10 years after discontinuation of estrogen plus progestin therapy and estrogen-alone therapy. Extension of the WHI trials also demonstrated increased breast cancer risk associated with estrogen plus progestin therapy. Observational studies also suggest that the risk of breast cancer was greater, and became apparent earlier, with estrogen plus progestin therapy as compared to estrogen-alone therapy. These studies have not generally found significant variation in the risk of breast cancer among different estrogen plus progestin combinations, doses, or routes of administration.

The use of estrogen-alone and estrogen plus progestin has been reported to result in an increase in abnormal mammograms requiring further evaluation.

All women should receive yearly breast examinations by a healthcare provider and perform monthly breast self-examinations. In addition, mammography examinations should be scheduled based on patient age, risk factors and prior mammogram results.

Endometrial Cancer

Endometrial hyperplasia (a possible precursor of endometrial cancer) has been reported to occur at a rate of approximately 1 percent or less with norethindrone acetate and ethinyl estradiol tablets.

An increased risk of endometrial cancer has been reported with the use of unopposed estrogen therapy in a woman with a uterus. The reported endometrial cancer risk among unopposed estrogen users is about 2 to 12 times greater than in non-users, and appears dependent on duration of treatment and on estrogen dose. Most studies show no significant increased risk associated with use of estrogens for less than 1 year. The greatest risk appears associated with prolonged use, with increased risks of 15- to 24-fold for 5 to 10 years or more. This risk has been shown to persist for at least 8 to 15 years after estrogen therapy is discontinued.

Clinical surveillance of all women using estrogen-alone or estrogen plus progestogen therapy is important. Adequate diagnostic measures, including directed or random endometrial sampling when indicated, should be undertaken to rule out malignancy in postmenopausal women with undiagnosed persistent or recurring abnormal genital bleeding.

There is no evidence that the use of natural estrogens results in a different endometrial risk profile than synthetic estrogens of equivalent estrogen dose. Adding a progestogen to estrogen therapy in postmenopausal women has been shown to reduce the risk of endometrial hyperplasia, which may be a precursor to endometrial cancer.

Ovarian Cancer

The CE plus MPA substudy of WHI reported that estrogen plus progestin increased the risk of ovarian cancer. After an average follow-up of 5.6 years, the relative risk for ovarian cancer for CE plus MPA versus placebo was 1.58 (95 percent CI, 0.77 to 3.24), but it was not statistically significant. The absolute risk for CE plus MPA versus placebo was 4 versus 3 cases per 10,000 women-years. ⁷

A meta-analysis of 17 prospective and 35 retrospective epidemiology studies found that women who used hormonal therapy for menopausal symptoms had an increased risk for ovarian cancer. The primary analysis, using case-control comparisons, included 12,110 cancer cases from the 17 prospective studies. The relative risks associated with current use of hormonal therapy was 1.41 (95% confidence interval [CI] 1.32 to 1.50); there was no difference in the risk estimates by duration of the exposure (less than 5 years [median of 3 years] vs. greater than 5 years [median of 10 years] of use before the cancer diagnosis). The relative risk associated with combined current and recent use (discontinued use within 5 years before cancer diagnosis) was 1.37 (95% CI 1.27 to 1.48), and the elevated risk was significant for both estrogen-alone and estrogen plus progestin products. The exact duration of hormone therapy use associated with an increased risk of ovarian cancer, however, is unknown.

In the WHI Memory Study (WHIMS) estrogen plus progestin ancillary study, a population of 4,532 postmenopausal women 65 to 79 years of age was randomized to daily CE (0.625 mg) plus MPA (2.5 mg) or placebo.

After an average follow-up of 4 years, 40 women in the CE plus MPA group and 21 women in the placebo group were diagnosed with probable dementia. The relative risk of probable dementia for CE plus MPA versus placebo was 2.05 (95 percent CI, 1.21 to 3.48). The absolute risk of probable dementia for CE plus MPA versus placebo was 45 versus 22 cases per 10,000 women-years ⁸ [see Use in Specific Populations (8.5 ), and Clinical Studies (14.6 )] .

In the WHIMS estrogen-alone ancillary study, a population of 2,947 hysterectomized women 65 to 79 years of age was randomized to daily CE (0.625 mg)-alone or placebo.

After an average follow-up of 5.2 years, 28 women in the estrogen-alone group and 19 women in the placebo group were diagnosed with probable dementia. The relative risk of probable dementia for CE-alone versus placebo was 1.49 (95 percent CI, 0.83 to 2.66). The absolute risk of probable dementia for CE-alone versus placebo was 37 versus 25 cases per 10,000 women-years ⁸ [see Use in Specific Populations (8.5 ), and Clinical Studies (14.6 )] .

When data from the two populations in the WHIMS estrogen-alone and estrogen plus progestin ancillary studies were pooled as planned in the WHIMS protocol, the reported overall relative risk for probable dementia was 1.76 (95 percent CI, 1.19 to 2.6). Since both ancillary substudies were conducted in women 65 to 79 years of age, it is unknown whether these findings apply to younger postmenopausal women ⁸ [see Use in Specific Populations (8.5 ), and Clinical Studies (14.6 )] .

A 2- to 4-fold increase in the risk of gallbladder disease requiring surgery in postmenopausal women receiving estrogens has been reported.

Estrogen administration may lead to severe hypercalcemia in women with breast cancer and bone metastases. Discontinue estrogens, including norethindrone acetate and ethinyl estradiol tablets, if hypercalcemia occurs, and take appropriate measures to reduce the serum calcium level.

Retinal vascular thrombosis has been reported in women receiving estrogens. Discontinue norethindrone acetate and ethinyl estradiol tablets pending examination if there is sudden partial or complete loss of vision, or a sudden onset of proptosis, diplopia, or migraine. Permanently discontinue estrogens, including norethindrone acetate and ethinyl estradiol tablets , if examination reveals papilledema or retinal vascular lesions.

Studies of the addition of a progestogen for 10 or more days of a cycle of estrogen administration or daily with estrogen in a continuous regimen, have reported a lowered incidence of endometrial hyperplasia than would be induced by estrogen treatment alone. Endometrial hyperplasia may be a precursor to endometrial cancer.

There are, however, possible risks that may be associated with the use of progestogens with estrogens compared to estrogen-alone regimens. These include an increased risk of breast cancer.

In a small number of case reports, substantial increases in blood pressure have been attributed to idiosyncratic reactions to estrogens. In a large, randomized, placebo-controlled clinical trial, a generalized effect of estrogen therapy on blood pressure was not seen.

In women with pre-existing hypertriglyceridemia, estrogen therapy may be associated with elevations of plasma triglycerides leading to pancreatitis. Discontinue norethindrone acetate and ethinyl estradiol tablets if pancreatitis occurs.

Estrogens may be poorly metabolized in women with hepatic impairment. Exercise caution in any women with a history of cholestatic jaundice associated with past estrogen use or with pregnancy. In the case of recurrence of cholestatic jaundice, discontinue norethindrone acetate and ethinyl estradiol tablets.

Estrogen administration leads to increased thyroid-binding globulin (TBG) levels. Women with normal thyroid function can compensate for the increased TBG by making more thyroid hormone, thus maintaining free T ₄ and T ₃ serum concentrations in the normal range. Women dependent on thyroid hormone replacement therapy who are also receiving estrogen may require increased doses of their thyroid replacement therapy. Monitor thyroid function in these women during treatment with norethindrone acetate and ethinyl estradiol tablets to maintain their free thyroid hormone levels in an acceptable range.

Estrogens plus progestogens may cause some degree of fluid retention. Monitor any women with condition(s) that might predispose her to fluid retention, such as cardiac or renal impairment. Discontinue estrogen plus progestogen therapy, including norethindrone acetate and ethinyl estradiol tablets, with evidence of medically concerning fluid retention.

Estrogen-induced hypocalcemia may occur in women with hypoparathyroidism. Consider whether the benefits of estrogen therapy, including norethindrone acetate and ethinyl estradiol tablets, outweigh the risks in such women.

A few cases of malignant transformation of residual endometrial implants have been reported in women treated post-hysterectomy with estrogen-alone therapy.

Exogenous estrogens may exacerbate symptoms of angioedema in women with hereditary angioedema. Consider whether the benefits of estrogen therapy, including norethindrone acetate and ethinyl estradiol tablets, outweigh the risks in such women.

Estrogen therapy, including norethindrone acetate and ethinyl estradiol tablets, may cause an exacerbation of asthma, diabetes mellitus, epilepsy, migraine, porphyria, systemic lupus erythematosus and hepatic hemangiomas. Consider whether the benefits of estrogen therapy outweigh the risks in women with such conditions.

Serum follicle stimulating hormone (FSH) and estradiol levels have not been shown to be useful in the management of postmenopausal women with moderate to severe vasomotor symptoms.

Accelerated prothrombin time, partial thromboplastin time, and platelet aggregation time; increased platelet count; increased factors II, VII antigen, VIII antigen, VIII coagulant activity, IX, X, XII, VII-X complex, II-VII-X complex, and beta-thromboglobulin; decreased levels of antifactor Xa and antithrombin III, decreased antithrombin III activity; increased levels of fibrinogen and fibrinogen activity; increased plasminogen antigen and activity.

Increased TBG levels leading to increased circulating total thyroid hormone levels as measured by protein-bound iodine (PBI), T ₄ levels (by column or by radioimmunoassay) or T ₃ levels by radioimmunoassay. T ₃ resin uptake is decreased, reflecting the elevated TBG. Free T ₄ and free T ₃ concentrations are unaltered. Women on thyroid replacement therapy may require higher doses of thyroid hormone.

Other binding proteins may be elevated in serum, for example, corticosteroid binding globulin (CBG), sex hormone-binding globulin (SHBG), leading to increased total circulating corticosteroids and sex steroids, respectively. Norethindrone acetate and ethinyl estradiol tablets 1/5 was associated with an SHBG increase of 22 percent. Free hormone concentrations, such as testosterone and estradiol, may be decreased. Other plasma proteins may be increased (angiotensinogen/renin substrate, alpha-1-antitrypsin, ceruloplasmin).

Increased plasma high-density lipoprotein (HDL) and HDL ₂ cholesterol subfraction concentrations, reduced low-density lipoprotein (LDL) cholesterol concentration, increased triglycerides levels.

Impaired glucose tolerance.

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Adverse reactions reported by ≥5 percent of women in controlled clinical studies of norethindrone acetate and ethinyl estradiol tablets are shown in Table 1.

Table 1. Associated Adverse Reactions Reported by ≥5 Percent of Women by Body System •

•The total number of women for each body system may be less than the number of women with AEs in that body system because a women may have had more than one AE per body system

The following additional adverse reactions have been identified during post-approval use of norethindrone acetate and ethinyl estradiol tablets. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Genitourinary System

Changes in vaginal bleeding pattern and abnormal withdrawal bleeding or flow; breakthrough bleeding; spotting; increase in size of uterine leiomyomata, vaginitis, including vaginal candidiasis; change in amount of cervical secretion; changes in cervical ectropion; ovarian cancer; endometrial hyperplasia; endometrial cancer; uterine cancer; vaginal hemorrhage; ovarian cyst; irregular menstruation; metrorrhagia; menorrhagia; dysmenorrhea; uterine enlargement.

Breasts

Tenderness, enlargement, breast pain, nipple pain, nipple discharge, galactorrhea; fibrocystic breast changes; breast cancer; breast disorder; breast mass; breast enlargement.

Cardiovascular

Deep and superficial venous thrombosis; pulmonary embolism; thrombophlebitis; thrombosis; chest pain; myocardial infarction; cerebrovascular accident (stroke); transient ischemic attack; hemiparesis; increase in blood pressure; irregular heart rate; palpitations; dyspnea.

Gastrointestinal

Nausea, vomiting; cholestatic jaundice; pancreatitis, enlargement of hepatic hemangiomas; bloating, abdominal cramps; abdominal pain; increased incidence of gallbladder disease; cholecystitis; cholelithiasis.

Skin

Chloasma or melasma that may persist when drug is discontinued; generalized erythema; erythema multiforme; erythema nodosum; hemorrhagic eruption; loss of scalp hair; hirsutism; rash, pruritus.

Eyes

Retinal vascular thrombosis; visual impairment; intolerance to contact lenses.

Central Nervous System (CNS)

Headache; migraine; dizziness; depression; chorea; nervousness; mood disturbances; irritability; exacerbation of epilepsy, dementia; paresthesia; insomnia.

Miscellaneous

Increase or decrease in weight; reduced carbohydrate tolerance; aggravation of porphyria; edema; arthralgias; leg cramps; back pain; changes in libido; urticaria, angioedema, anaphylactoid/anaphylactic reactions; hypocalcemia; exacerbation of asthma; increased triglycerides; blood glucose abnormal; fatigue; myalgia; hypersensitivity.

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, which is secreted by the adrenal cortex, to estrone in the peripheral tissues. Thus, estrone and the sulfate conjugated form, estrone sulfate, are the most abundant circulating estrogens in postmenopausal women. The pharmacologic effects of ethinyl estradiol are similar to those of endogenous estrogens.

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 FSH through a negative feedback mechanism. Estrogens act to reduce the elevated levels of these hormones seen in postmenopausal women.

Progestin compounds enhance cellular differentiation and generally oppose the actions of estrogens by decreasing estrogen receptor levels, increasing local metabolism of estrogens to less active metabolites, or inducing gene products that blunt cellular responses to estrogen. Progestins exert their effects in target cells by binding to specific progesterone receptors that interact with progesterone response elements in target genes. Progesterone receptors have been identified in the female reproductive tract, breast, pituitary, hypothalamus, bone, skeletal tissue and central nervous system. Progestins produce similar endometrial changes to those of the naturally occurring hormone progesterone.

Generally, a serum estrogen concentration does not predict an individual woman’s therapeutic response to norethindrone acetate and ethinyl estradiol tablets nor her risk for adverse outcomes. Likewise, exposure comparisons across different estrogen products to infer efficacy or safety for the individual woman may not be valid.

Absorption

Norethindrone acetate (NA) is completely deacetylated to norethindrone after oral administration, and the disposition of norethindrone acetate is indistinguishable from that of orally administered norethindrone. Norethindrone acetate and ethinyl estradiol (EE) are absorbed from norethindrone acetate and ethinyl estradiol tablets, with maximum plasma concentrations of norethindrone and ethinyl estradiol generally occurring 1 to 2 hours postdose. Both are subject to first-pass metabolism after oral dosing, resulting in an absolute bioavailability of approximately 64 percent for norethindrone and 55 percent for ethinyl estradiol. Bioavailability of norethindrone acetate and ethinyl estradiol tablets is similar to that from solution for norethindrone and slightly less for ethinyl estradiol. Administration of norethindrone acetate and ethinyl estradiol tablets with a high fat meal decreases rate but not extent of ethinyl estradiol absorption. The extent of norethindrone absorption is increased by 27 percent following administration of norethindrone acetate and ethinyl estradiol tablets with food.

The full pharmacokinetic profile of norethindrone acetate and ethinyl estradiol tablets was not characterized due to assay sensitivity limitations. However, the multiple-dose pharmacokinetics were studied at a dose of 1 mg NA/10 mcg EE in 18 post-menopausal women. Mean plasma concentrations are shown below (Figure 1) and pharmacokinetic parameters are found in Table 2. Based on a population pharmacokinetic analysis, mean steady-state concentrations of norethindrone for 1 mg NA/5 mcg EE and 1/10 are slightly more than proportional to dose when compared to 0.5 mg NA/2.5 mcg EE tablets. It can be explained by higher SHBG concentrations. Mean steady-state plasma concentrations of ethinyl estradiol for the norethindrone acetate and ethinyl estradiol 0.5 /2.5 tablets and norethindrone acetate and ethinyl estradiol 1 /5 tablets are proportional to dose, but there is a less than proportional increase in steady-state concentrations for the NA/EE 1 /10 tablet.

Figure 1. Mean Steady-State (Day 87) Plasma Norethindrone and Ethinyl Estradiol Concentrations Following Continuous Oral Administration of 1 mg NA/10 mcg EE Tablets

^† C _max = Maximum plasma concentration; t _max = time of C _max ; AUC (0 to 24) = Area under the plasma concentration-time curve over the dosing interval; and CL/F = Apparent oral clearance;

t _½ = Elimination half-life

^‡ ND = Not determined

Based on a population pharmacokinetic analysis, average steady-state concentrations (Css) of norethindrone and ethinyl estradiol for norethindrone acetate and ethinyl estradiol 1/5 tablets are estimated to be 2.6 ng/mL and 11.4 pg/mL, respectively. Css values of norethindrone and ethinyl estradiol for norethindrone acetate and ethinyl estradiol 0.5/2.5 tablets are estimated to be 1.1 ng/mL and 5.4 ng/mL, respectively.

The pharmacokinetics of ethinyl estradiol and norethindrone acetate were not affected by age, (age range 40 to 62 years), in the postmenopausal population studied.

Distribution

The 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 SHBG and albumin.

Volume of distribution of norethindrone and ethinyl estradiol ranges from 2 to 4 L/kg. Plasma protein binding of both steroids is extensive (greater than 95 percent); norethindrone binds to both albumin and SHBG, whereas ethinyl estradiol binds only to albumin. Although ethinyl estradiol does not bind to SHBG, it induces SHBG synthesis.

Metabolism

Exogenous 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 a 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 intestine 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.

Norethindrone undergoes extensive biotransformation, primarily via reduction, followed by sulfate and glucuronide conjugation. The majority of metabolites in the circulation are sulfates, with glucuronides accounting for most of the urinary metabolites. A small amount of norethindrone acetate is metabolically converted to ethinyl estradiol, such that exposure to ethinyl estradiol following administration of 1 mg of norethindrone acetate is equivalent to oral administration of 2.8 mcg ethinyl estradiol. Ethinyl estradiol is also extensively metabolized, both by oxidation and by conjugation with sulfate and glucuronide. Sulfates are the major circulating conjugates of ethinyl estradiol and glucuronides predominate in urine. The primary oxidative metabolite is 2-hydroxy ethinyl estradiol, formed by the CYP3A4 isoform of cytochrome P450. Part of the first-pass metabolism of ethinyl estradiol is believed to occur in gastrointestinal mucosa. Ethinyl estradiol may undergo enterohepatic circulation.

Excretion

Estradiol, estrone, and estriol are excreted in the urine along with glucuronide and sulfate conjugates.

Norethindrone and ethinyl estradiol are excreted in both urine and feces, primarily as metabolites. Plasma clearance values for norethindrone and ethinyl estradiol are similar (approximately 0.4 L/hr/kg). Steady-state elimination half-lives of norethindrone and ethinyl estradiol following administration of 1 mg NA/10 mcg EE tablets are approximately 13 hours and 24 hours, respectively.

Long-term continuous administration of natural and synthetic estrogens in certain animal species increases the frequency of carcinomas of the breast, uterus, cervix, vagina, testis, and liver.

A 12-week placebo-controlled, multicenter, randomized clinical trial was conducted in 266 symptomatic women who had at least 56 moderate to severe hot flushes during the week prior to randomization. On average, women had 12 hot flushes per day upon study entry.

A total of 66 women were randomized to receive norethindrone acetate and ethinyl estradiol tablets 1/5 and 66 women were randomized to the placebo group. Norethindrone acetate and ethinyl estradiol tablets 1/5 was shown to be statistically better than placebo at weeks 4, and 12 for relief of the frequency of moderate to severe vasomotor symptoms (see Table 3). In Table 4, norethindrone acetate and ethinyl estradiol tablets 1 /5 was shown to be statistically better than placebo at weeks 4 and 12 for relief of the severity of moderate to severe vasomotor symptoms.

Table 3. Mean Change from Baseline in the Number of Moderate to Severe Vasomotor Symptoms per Week -ITT Population, LOCF

^è Denotes statistical significance at the 0.05 level

• [1] The baseline number of moderate to severe vasomotor symptoms (MSVS) is the weekly average number of MSVS during the two week pre-randomization observation period.

[2] ANCOVA -Analysis of Covariance model where the observation variable is change from baseline; independent variables include treatment, center and baseline as covariate. The 95 percent CI -Mann-Whitney confidence interval for the difference between means (not stratified by center). ITT = intent to treat; LOCF last observation carried forward; CI = confidence interval 2 randomized subjects (1 in Placebo and 1 in norethindrone acetate and ethinyl estradiol tablets) did not return diaries.

Table 4. Mean Change from Baseline in the Daily Severity Score of Moderate to Severe
Vasomotor Symptoms per Week - ITT Population, LOCF

^¥ Denotes statistical significance at the 0.05 level

[1] The baseline severity of moderate to severe vasomotor symptoms (MSVS) is the daily severity score of MSVS during the two week pre-randomization observation period.

[2] ANCOVA - Analysis of Covariance model where the observation variable is change from baseline; independent variables include treatment, center and baseline as covariate. The 95 percent CI - Mann-Whitney confidence interval for the difference between means (not stratified by center).

ITT = intent to treat; LOCF = last observation carried forward; CI = confidence interval 2 randomized women (1 in Placebo and 1 in norethindrone acetate and ethinyl estradiol tablets) did not return diaries.

A 2-year, placebo-controlled, multicenter, randomized clinical trial was conducted to determine the safety and efficacy of norethindrone acetate and ethinyl estradiol tablets on maintaining bone mineral density, protecting the endometrium, and to determine effects on lipids. A total of 1,265 women were enrolled and randomized to either placebo, 0.2 mg NA/1 mcg ethinyl estradiol (NA/EE 0.2 /1), 0.5 mg NA/2.5 mcg EE (NA/EE 0.5 /2.5), norethindrone acetate and ethinyl estradiol tablets 1/5 and 1 mg NA/10 mcg EE (NA/EE 1/10) or matching unopposed EE doses (1, 2.5, 5, or 10 mcg) for a total of 9 treatment groups. All participants received 1000 mg of calcium supplementation daily. Of the 1,265 women randomized to the various treatment arms of this study, 137 were randomized to placebo, 146 to norethindrone acetate and ethinyl estradiol tablets 1/5, 136 to NA/EE 0.5/2.5 and 141 to EE 5 mcg and 137 to EE 2.5 mcg. Of these, 134 placebo, 143 norethindrone acetate and ethinyl estradiol tablets 1/5, 136 NA/EE 0.5/2.5, 139 EE 5 mcg and 137 EE 2.5 mcg had a baseline endometrial result. Baseline biopsies were classified as normal (in approximately 95 percent of subjects), or insufficient tissue (in approximately 5 percent of subjects). Follow-up biopsies were obtained in approximately 70 to 80 percent of patients in each arm after 12 and 24 months of therapy. Results for norethindrone acetate and ethinyl estradiol tablets 1/5 and appropriate comparators are shown in Table 5.

Table 5. Endometrial Biopsy Results After 12 and 24 Months of Treatment (CHART Study, 376-359)

^• All patients with endometrial hyperplasia were carried forward for all time points.

The cumulative incidence of amenorrhea, defined as no bleeding or spotting obtained from participant recall, was evaluated over 12 months for norethindrone acetate and ethinyl estradiol tablets 1/5 and placebo arms. Results are shown in Figure 2.

Figure 2. Participants with Cumulative Amenorrhea Over Time: Intent-to-Treat Population, Last Observation Carried Forward

In the 2 year study, trabecular BMD was assessed at lumbar spine using quantitative computed tomography. A total of 419 postmenopausal primarily Caucasian women, 40 to 64 years of age, with intact uteri and non-osteoporotic bone mineral densities were randomized (1:1:1) to norethindrone acetate and ethinyl estradiol tablets 1/5, NA/EE 0.5/2.5 or placebo. Approximately 75 percent of the women in each group completed the two-year study. All women received 1000 mg calcium in divided doses. Vitamin D was not supplemented.

As shown in Figure 3, women treated with norethindrone acetate and ethinyl estradiol tablets 1/5 had an average increase of 3.1 percent in lumbar spine BMD from baseline to Month 24. Women treated with placebo had average decreases of –6.3 percent in spinal BMD from baseline to Month 24. The differences in the changes from baseline to Month 24 in the norethindrone acetate and ethinyl estradiol tablets 1/5 group compared with the placebo group was statistically significant.

Figure 3. Mean Percent Change (+ SE) From Baseline in Volumetric Bone Mineral Density• at Lumbar Spine Measured by Quantitative Computed Tomography after 12 and 24 Months of Treatment (Intent-to-Treat Population)

•It should be noted that when measured by QCT, BMD gains and losses are greater than when measured by dual X-ray absorptiometry (DXA). Therefore, the differences in the changes in BMD between the placebo and active drug treated groups will be larger when measured by QCT compared with DXA. Changes in BMD measured by DXA should not be compared with changes in BMD measured by QCT.

The WHI enrolled approximately 27,000 predominantly healthy postmenopausal women in two substudies to assess the risks and benefits of daily oral CE (0.625 mg)-alone or in combination with MPA (2.5 mg) compared to placebo in the prevention of certain chronic diseases. The primary endpoint was the incidence of CHD (defined as nonfatal MI, silent MI and CHD death), with invasive breast cancer as the primary adverse outcome. A “global index” included the earliest occurrence of CHD, invasive breast cancer, stroke, PE, endometrial cancer (only in the CE plus MPA substudy), colorectal cancer, hip fracture, or death due to other cause. The study did not evaluate the effects of CE plus MPA or CE-alone on menopausal symptoms.

WHI Estrogen Plus Progestin Substudy

The WHI estrogen plus progestin substudy was stopped early. According to the predefined stopping rule, after an average follow-up of 5.6 years of treatment, the increased risk of invasive breast cancer and cardiovascular events exceeded the specified benefits included in the “global index”. The absolute excess risk of events included in the “global index” was 19 per 10,000 women-years.

For those outcomes included in the WHI “global index” that reached statistical significance after 5.6 years of follow-up, the absolute excess risks per 10,000 women-years in the group treated with CE plus MPA were 7 more CHD events, 8 more strokes, 10 more PEs, and 8 more invasive breast cancers, while the absolute risk reductions per 10,000 women-years were 6 fewer colorectal cancers and 5 fewer hip fractures.

Results of the CE plus MPA substudy, which included 16,608 women (average 63 years of age, range 50 to 79; 83.9 percent White, 6.8 percent Black, 5.4 percent Hispanic, 3.9 percent Other) are presented in Table 6. These results reflect centrally adjudicated data after an average follow-up of 5.6 years.

Table 6. Relative and Absolute Risk Seen in the Estrogen Plus Progestin Substudy of WHI at an Average of 5.6 Years ^{¶ #Ϸ}

^¶ Adapted from numerous WHI publications. WHI publications can be viewed at www.nhlbi.nih.gov/whi.

^#Ϸ Results are based on centrally adjudicated data.

^ß Nominal confidence intervals unadjusted for multiple looks and multiple comparisons.

^à Not included in "global index".

^ẻ Includes metastic and non-metastic breast cancer with the exception of in situ cancer.

^ð All deaths, except from breast or colorectal cancer, definite or probable CHD, PE or cerebrovascular disease.

^ø 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, colorectal cancer, hip fracture, or death due to other causes.

Timing of the initiation of estrogen plus progestin therapy relative to the start of menopause may affect the overall risk benefit profile. The WHI estrogen plus progestin substudy stratified by age showed in women 50 to 59 years of age, a non-significant trend toward reduced risk for overall mortality [( hazard ratio (HR) 0.69 (95 percent CI, 0.44 to 1.07) ].

WHI Estrogen-Alone Substudy

The WHI estrogen-alone substudy was also stopped early because an increased risk of stroke was observed, and it was deemed that no further information would be obtained regarding the risks and benefits of estrogen-alone in predetermined primary endpoints.

Results of the estrogen-alone substudy, which included 10,739 women (average 63 years of age, range 50 to 79; 75.3 percent White, 15.1 percent Black, 6.1 percent Hispanic, 3.6 percent Other), after an average follow-up of 7.1 years, are presented in Table 7.

Table 7. Relative and Absolute Risk Seen in the Estrogen-Alone Substudy of WHI ^¥

^¥ Adapted from numerous WHI publications. WHI publications can be viewed at www.nblbi.nih.gov/whi .

^CE Nominal confidence intervals unadjusted for multiple looks and multiple comparisons.

^ce Results are based on centrally adjudicated data for an average follow-up of 7.1 years.

^Đ Not included in "global index".

• Results are based on an average follow-up of 6.8 years.

^† All deaths, except from breast or colorectal cancer, definite or probable CHD, PE or cerebrovascular disease.

^‡ 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, colorectal cancer, hip fracture, or death due to other causes.

For those outcomes included in the WHI “global index” that reached statistical significance, the absolute excess risk per 10,000 women-years in the group treated with CE-alone were 12 more strokes, while the absolute risk reduction per 10,000 women-years was 7 fewer hip fractures. ⁹ The absolute excess risk of events included in the “global index” was a non- significant 5 events per 10,000 women-years. There was no difference between the groups in terms of all-cause mortality.

No overall difference for primary CHD events (nonfatal MI, silent MI and CHD death) and invasive breast cancer incidence in women receiving CE-alone compared with placebo was reported in final centrally adjudicated results from the estrogen-alone substudy, after an average follow-up of 7.1 years (see Table 7).

Centrally adjudicated results for stroke events from the estrogen-alone substudy, after an average follow-up of 7.1 years, reported no significant difference in distribution of stroke subtype or severity, including fatal strokes, in women receiving CE-alone compared to placebo. Estrogen-alone therapy increased the risk of ischemic stroke, and this excess was present in all subgroups of women examined ¹⁰ (see Table 7).

Timing of the initiation of estrogen-alone therapy relative to the start of menopause may affect the overall risk benefit profile. The WHI estrogen-alone substudy stratified by age, showed in women 50 to 59 years of age a non-significant trend toward reduced risk for CHD [ HR 0.63 (95 percent CI, 0.36 to 1.09) ] and overall mortality [HR 0.71 ( 95 percent CI, 0.46 to 1.11 )].

The WHIMS estrogen plus progestin ancillary study of WHI enrolled 4,532 predominantly healthy postmenopausal women 65 years of age and older (47 percent were 65 to 69 years of age, 35 percent were 70 to 74 years of age, and 18 percent were 75 years of age and older) to evaluate the effects of CE (0.625 mg) plus MPA (2.5 mg) on the incidence of probable dementia (primary outcome) compared to placebo.

After an average follow-up of 4 years, the relative risk of probable dementia for CE plus MPA versus placebo was 2.05 (95 percent CI, 1.21 to 3.48). The absolute risk of probable dementia for CE plus MPA versus placebo was 45 versus 22 per 10,000 women-years. Probable dementia as defined in this study included Alzheimer’s disease (AD), vascular dementia (VaD) and mixed types (having features of both AD and VaD). The most common classification of probable dementia in the treatment group and the placebo group was AD. Since the ancillary study was conducted in women 65 to 79 years of age, it is unknown whether these findings apply to younger postmenopausal women [ see Warnings and Precautions (5.3 ) , and Use in Specific Populations (8.5 ) ].

The WHIMS estrogen-alone ancillary study of WHI enrolled 2,947 predominantly healthy hysterectomized postmenopausal women 65 to 79 years of age and older (45 percent were 65 to 69 years of age; 36 percent were 70 to 74 years of age; 19 percent were 75 years of age and older) to evaluate the effects of daily CE (0.625 mg)-alone on the incidence of probable dementia (primary outcome) compared to placebo.

After an average follow-up of 5.2 years, the relative risk of probable dementia for CE-alone versus placebo was 1.49 (95 percent CI, 0.83 to 2.66). The absolute risk of probable dementia for CE-alone versus placebo was 37 versus 25 cases per 10,000 women-years. Probable dementia as defined in this study included AD, VaD and mixed types (having features of both AD and VaD). The most common classification of probable dementia in the treatment group and the placebo group was AD. Since the ancillary study was conducted in women 65 to 79 years of age, it is unknown whether these findings apply to younger postmenopausal women [see Warnings and Precautions (5.3 ) , and Use in Specific Populations (8.5 )].

When data from the two populations were pooled as planned in the WHIMS protocol, the reported overall relative risk for probable dementia was 1.76 (95 percent CI, 1.19 to 2.6). Differences between groups became apparent in the first year of treatment. It is unknown whether these findings apply to younger postmenopausal women [see Warnings and Precautions (5.3 ) , and Use in Specific Populations (8.5 )] .

Norethindrone Acetate and Ethinyl Estradiol Tablets, USP are available in the following strengths and package sizes:

Norethindrone Acetate and Ethinyl Estradiol Tablets, USP 0.5 mg/2.5 mcg, are light pink to pink, round, flat-faced, beveled edge, uncoated, tablets debossed with “D5” on one side and plain on the other side. Each tablet contains 0.5 mg norethindrone acetate, USP and 2.5 mcg ethinyl estradiol, USP and are available as:

NDC 68462-656-90 Bottle of 90 Tablets

1. NDC 68462-656-29 1 carton containing 3 individual foil pouches (68462-656-84). Each pouch contains 1 blister of 28 tablets (68462-656-84)

Norethindrone Acetate and Ethinyl Estradiol Tablets, USP 1 mg/5 mcg are white to off-white, round, flat-faced, beveled edge, uncoated tablets debossed with “D6” on one side plain on the other side. Each tablet contains 1 mg norethindrone acetate, USP and 5 mcg ethinyl estradiol, USP and are available as:

NDC 68462-657-90 Bottle of 90 Tablets

1. NDC 68462-657-29 1 carton containing 3 individual foil pouches (68462-657-84). Each pouch contains 1 blister of 28 tablets (68462-657-84).

Store at 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C to 30°C (59°F to 86°F) [See USP Controlled Room Temperature].

Keep norethindrone acetate and ethinyl estradiol tablets out of the reach of children.