Norethindrone Acetate

NORETHINDRONE ACETATE- norethindrone acetate tablet
Amneal Pharmaceuticals LLC

DESCRIPTION

Norethindrone acetate tablets, USP — 5 mg oral tablets.

Norethindrone acetate, USP (17-hydroxy-19-nor-17α-pregn-4-en-20-yn-3-one acetate), a synthetic, orally active progestin, is the acetic acid ester of norethindrone, USP. It is a white, or creamy white, crystalline powder.

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Norethindrone acetate tablets, USP contain the following inactive ingredients: lactose, magnesium stearate, and microcrystalline cellulose.

CLINICAL PHARMACOLOGY

Norethindrone acetate induces secretory changes in an estrogen-primed endometrium. On a weight basis, it is twice as potent as norethindrone.

Pharmacokinetics

Absorption

Norethindrone acetate is completely and rapidly deacetylated to norethindrone (NET) after oral administration, and the disposition of norethindrone acetate is indistinguishable from that of orally administered norethindrone. Norethindrone acetate is rapidly absorbed from norethindrone acetate tablets, with maximum plasma concentration of norethindrone generally occurring at about 2 hours post-dose. The pharmacokinetic parameters of norethindrone following single oral administration of norethindrone acetate in 29 healthy female volunteers are summarized in Table 1.

Table 1.Pharmacokinetic Parameters after a Single Dose of Norethindrone Acetate in Healthy Women
Norethindrone Acetate (n=29) Arithmetic Mean ± SD
Norethindrone (NET)
AUC = area under the curve,
Cmax = maximum plasma concentration,
tmax = time at maximum plasma concentration,
t1/2 = half-life,
SD = standard deviation
AUC (0-inf) (ng/ml*h) 166.90 ± 56.28
Cmax (ng/ml) 26.19 ± 6.19
tmax (h) 1.83 ± 0.58
t1/2 (h) 8.51 ± 2.19

Figure 1. Mean Plasma Concentration Profile after a Single Dose of 5 mg Administered to 29 Healthy Female Volunteers under Fasting Conditions

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Effect of Food

The effect of food administration on the pharmacokinetics of norethindrone acetate has not been studied.

Distribution

Norethindrone is 36% bound to sex hormone-binding globulin (SHBG) and 61% bound to albumin. Volume of distribution of norethindrone is about 4 L/kg.

Metabolism

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.

Excretion

Plasma clearance value for norethindrone is approximately 0.4 L/hr/kg. Norethindrone is excreted in both urine and feces, primarily as metabolites. The mean terminal elimination half-life of norethindrone following a single dose administration of norethindrone acetate is approximately 9 hours.

Special Populations

Geriatrics

The effect of age on the pharmacokinetics of norethindrone after norethindrone acetate administration has not been evaluated.

Race

The effect of race on the disposition of norethindrone after norethindrone acetate administration has not been evaluated.

Renal Insufficiency

The effect of renal disease on the disposition of norethindrone after norethindrone acetate administration has not been evaluated. In premenopausal women with chronic renal failure undergoing peritoneal dialysis who received multiple doses of an oral contraceptive containing ethinyl estradiol and norethindrone, plasma norethindrone concentration was unchanged compared to concentrations in premenopausal women with normal renal function.

Hepatic Insufficiency

The effect of hepatic disease on the disposition of norethindrone after norethindrone acetate administration has not been evaluated. However, norethindrone acetate is contraindicated in markedly impaired liver function or liver disease.

Drug Interactions

No pharmacokinetic drug interaction studies investigating any drug-drug interactions with norethindrone acetate have been conducted.

INDICATIONS AND USAGE

Norethindrone acetate tablets, USP is indicated for the treatment of secondary amenorrhea, endometriosis, and abnormal uterine bleeding due to hormonal imbalance in the absence of organic pathology, such as submucous fibroids or uterine cancer. Norethindrone acetate tablets, USP are not intended, recommended or approved to be used with concomitant estrogen therapy in postmenopausal women for endometrial protection.

CONTRAINDICATIONS

  • Known or suspected pregnancy. There is no indication for norethindrone acetate, USP in pregnancy. (See PRECAUTIONS.)
  • Undiagnosed vaginal bleeding
  • Known, suspected or history of cancer of the breast
  • Active deep vein thrombosis, pulmonary embolism or history of these conditions
  • Active or recent (e.g., within the past year) arterial thromboembolic disease (e.g., stroke, myocardial infarction)
  • Impaired liver function or liver disease
  • As a diagnostic test for pregnancy
  • Hypersensitivity to any of the drug components

WARNINGS

1. Cardiovascular disorders

Patients with risk factors for arterial vascular disease (e.g., hypertension, diabetes mellitus, tobacco use, hypercholesterolemia, and obesity) and/or venous thromboembolism (e.g., personal history or family history of VTE, obesity, and systemic lupus erythematosus) should be managed appropriately.

2. Visual abnormalities

Discontinue medication pending examination if there is a sudden partial or complete loss of vision or if there is sudden onset of proptosis, diplopia, or migraine. If examination reveals papilledema or retinal vascular lesions, medication should be discontinued.

PRECAUTIONS

General Precautions

  • Because this drug may cause some degree of fluid retention, conditions which might be influenced by this factor, such as epilepsy, migraine, cardiac or renal dysfunctions, require careful observation.
  • In cases of breakthrough bleeding, and in all cases of irregular bleeding per vagina, nonfunctional causes should be borne in mind. In cases of undiagnosed vaginal bleeding, adequate diagnostic measures are indicated.
  • Patients who have a history of clinical depression should be carefully observed and the drug discontinued if the depression recurs to a serious degree.
  • Data suggest that progestin therapy may have adverse effects on lipid and carbohydrate metabolism. The choice of progestin, its dose, and its regimen may be important in minimizing these adverse effects, but these issues will require further study before they are clarified. Women with hyperlipidemias and/or diabetes should be monitored closely during progestin therapy.
  • The pathologist should be advised of progestin therapy when relevant specimens are submitted.

Information for the Patient

Healthcare providers are advised to discuss the PATIENT INFORMATION leaflet with patients for whom they prescribe norethindrone acetate.

Drug/Laboratory Test Interactions

The following laboratory test results may be altered by the use of estrogen/progestin combination drugs:

  1. 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.
  2. Increased thyroid-binding globulin (TBG) levels leading to increased circulating total thyroid hormone levels as measured by protein-bound iodine (PBI), T4 levels (by column or by radioimmunoassay) or T3 levels by radioimmunoassay. T3 resin uptake is decreased, reflecting the elevated TBG. Free T4 and free T3 concentrations are unaltered. Patients on thyroid replacement therapy may require higher doses of thyroid hormone.
  3. Other binding proteins may be elevated in serum (i.e., corticosteroid binding globulin (CBG), sex hormone binding globulin (SHBG)) leading to increased circulating corticosteroid and sex steroids, respectively. Free or biologically active hormone concentrations are unchanged. Other plasma proteins may be increased (angiotensinogen/renin substrate, alpha-1-antitrypsin, ceruloplasmin).
  4. Increased plasma HDL and HDL2 cholesterol subfraction concentrations, reduced LDL cholesterol concentration, increased triglycerides levels.
  5. Impaired glucose metabolism.
  6. Reduced response to metyrapone test.

Carcinogenesis, Mutagenesis, Impairment of Fertility

Some beagle dogs treated with medroxyprogesterone acetate developed mammary nodules. Although nodules occasionally appeared in control animals, they were intermittent in nature, whereas nodules in treated animals were larger and more numerous, and persisted. There is no general agreement as to whether the nodules are benign or malignant. Their significance with respect to humans has not been established.

Pregnancy

Pregnancy Category X

Norethindrone acetate is contraindicated during pregnancy as it may cause fetal harm when administered to pregnant women. Several reports suggest an association between intrauterine exposure to progestational drugs in the first trimester of pregnancy and congenital abnormalities in male and female fetuses. Some progestational drugs induce mild virilization of the external genitalia of female fetuses.

Nursing Mothers

Detectable amounts of progestins have been identified in the milk of mothers receiving them. Caution should be exercised when progestins are administered to a nursing woman.

Pediatric Use

Norethindrone acetate tablets are not indicated in children.

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