Norethindrone Acetate And Ethinyl Estradiol And Ferrous Fumarate

Introduction Overview

Generic Name

norethindrone acetate and ethinyl estradiol and ferrous fumarate

Brand Name

Junel Fe 24

Dosage Form

tablets

Drug Class

Contraceptives

Pharmacokinetics

Absorption:
Junel Fe 24 combines norethindrone acetate, a progestin, and ethinyl estradiol, an estrogen, administered orally. After ingestion, norethindrone acetate is rapidly and completely deacetylated to norethindrone, resulting in pharmacokinetics indistinguishable from norethindrone itself. Both norethindrone and ethinyl estradiol are rapidly absorbed, reaching peak plasma concentrations between 1 to 4 hours post-dose. Both compounds undergo significant first-pass hepatic metabolism, leading to absolute bioavailabilities of approximately 64% for norethindrone and about 43% for ethinyl estradiol. Administration with food modestly decreases the peak plasma concentrations of norethindrone (by approximately 11%) and ethinyl estradiol (by approximately 30%), while increasing norethindrone's overall absorption by 27%. This pharmacokinetic profile supports consistent systemic exposure, allowing for administration without regard to meals.

Distribution:
Norethindrone and ethinyl estradiol exhibit a volume of distribution ranging from 2 to 4 L/kg. Both compounds have high plasma protein binding exceeding 95%. Norethindrone binds mainly to albumin and sex hormone-binding globulin (SHBG), whereas ethinyl estradiol binds primarily to albumin and notably induces hepatic synthesis of SHBG, which can influence the pharmacokinetics of endogenous and exogenous steroids. This interaction leads to an observed increase in mean SHBG concentrations by approximately 150% from baseline levels during steady-state dosing, reflecting the estrogenic effects of ethinyl estradiol in Junel Fe 24.

Metabolism:
Norethindrone undergoes extensive hepatic metabolism primarily via reduction, followed by conjugation reactions including sulfate and glucuronide formation. The majority of circulating metabolites are sulfates, whereas glucuronides predominate in urine excretion. Ethinyl estradiol is extensively metabolized through cytochrome P450 3A4 (CYP3A4)-mediated oxidative pathways, predominantly forming 2-hydroxy ethinyl estradiol, along with conjugation reactions (sulfation and glucuronidation). The metabolism of ethinyl estradiol also involves significant first-pass effects within the gastrointestinal mucosa and undergoes enterohepatic recycling, contributing to sustained systemic exposure.

Elimination:
Both norethindrone and ethinyl estradiol are eliminated via renal and fecal routes primarily as metabolites. Plasma clearance rates approximate 0.4 L/hr/kg for both agents. The apparent terminal elimination half-life for norethindrone is around 8 hours, while ethinyl estradiol has a longer half-life of approximately 14 hours during repeated dosing with Junel Fe 24. Steady-state pharmacokinetics are typically reached by day 17 for norethindrone and by day 13 for ethinyl estradiol under multiple dosing regimens. These parameters support once-daily dosing to maintain effective contraceptive hormone levels.

Dosage Forms

Available Dosage Forms:
Junel Fe 24 is provided as oral tablets packaged in blister packs comprising 28 tablets per pack:
- 24 active light yellow tablets: Each contains 1 mg norethindrone acetate and 0.02 mg ethinyl estradiol.
- 4 inactive brown tablets: Each contains 75 mg ferrous fumarate (non-hormonal, serving as a reminder and providing iron supplementation, but without therapeutic contraceptive action).

Dosages for Adults and Adolescents:
- The recommended dosing regimen is one tablet orally once daily at the same time each day for 28 consecutive days.
- Active hormone-containing tablets are taken for 24 days followed by 4 days of ferrous fumarate inactive tablets.
- Junel Fe 24 may be initiated using either a Day 1 start (first day of menstrual bleeding) or Sunday start (first Sunday after onset of menses).
- For Sunday starts in initial cycles, backup contraception is advised for 7 days.
- Missed active tablets have specific management instructions depending on which week and how many were missed, with recommendations for additional contraception if dosing is significantly disrupted.

Specific Patient Populations:
- Safety and efficacy have been established in postpubertal adolescents and adult women of reproductive age; efficacy is similar in adolescents under 18 years.
- Use is contraindicated in women with BMI greater than 35 kg/m2, as efficacy has not been evaluated.
- Not indicated for use before menarche, in postmenopausal women, or in those with significant hepatic impairment.
- Lactating women should be counseled that Junel Fe 24 may reduce milk production and alternative contraceptive measures are recommended.
- Use in women with hepatic impairment is not studied; COCs metabolized by the liver may accumulate, requiring clinical monitoring.
- Dosing does not need adjustment for renal impairment; however, pharmacokinetics in these patients have not been studied.

The tablets are round, 6 mm in size, with active tablets debossed with “b” and “977,” and inactive tablets with “b” and “247” for identification. The ferrous fumarate tablets do not have contraceptive effects but help mitigate iron deficiency during menstruation.

Mechanism Of Action

Junel Fe 24 exerts its contraceptive effect primarily through the combined actions of its two hormonal components: norethindrone acetate, a progestin, and ethinyl estradiol, an estrogen. The principal mechanism of action is suppression of ovulation. By delivering steady levels of synthetic hormones, Junel Fe 24 inhibits the hypothalamic-pituitary-ovarian axis, preventing the mid-cycle surge of luteinizing hormone (LH) required for ovulation. Consequently, ovulation is effectively suppressed, reducing the possibility of fertilization.

In addition to ovulation inhibition, the progestin component modifies the cervical mucus, increasing its viscosity and creating a barrier to sperm penetration. This biochemical alteration impedes the motility and access of sperm to the ovum, thereby contributing an additional contraceptive effect. Furthermore, the endometrial lining undergoes changes under the influence of combined hormones, becoming less suitable for implantation of a fertilized egg, which offers an alternative contraceptive mechanism.

Norethindrone acetate is rapidly deacetylated in vivo to norethindrone, which binds to progesterone receptors throughout reproductive tissues, exerting its progestational effects. Ethinyl estradiol binds to estrogen receptors, mediating feedback inhibition on gonadotropin secretion and enhancing progestin receptor expression, which helps stabilize the endometrial lining and supports the contraceptive effect.

Compared to other combined oral contraceptives (COCs) with higher doses or different progestins, Junel Fe 24 uses a relatively low estrogen dose of 0.02 mg ethinyl estradiol and a modest 1 mg dose of norethindrone acetate, balancing contraceptive efficacy with a reduced risk of estrogen-related adverse effects. Clinical studies demonstrate its effectiveness in preventing pregnancy with a Pearl Index of approximately 1.82, indicating reliable ovulation inhibition and contraceptive protection.

Research into the molecular pathways confirms the suppression of gonadotropins, alteration of intravascular factors affecting coagulation, and changes in the metabolic milieu induced by these hormones. The combination of these effects results in safe and reversible contraception when taken as directed. Moreover, Junel Fe 24's mechanism supports the maintenance of predictable withdrawal bleeding during the hormone-free interval induced by the ferrous fumarate inert tablets, enhancing user compliance and acceptability.

Pharmacological Actions

Suppresses ovulation through inhibition of luteinizing hormone (LH) surge
Thickens cervical mucus to impede sperm penetration and mobility
Alters endometrial lining, reducing likelihood of implantation
Provides exogenous estrogen and progestin to maintain hormonal balance
Increases sex hormone-binding globulin (SHBG), influencing free hormone levels
Exerts metabolic effects on carbohydrate and lipid metabolism
Modifies coagulation factors, increasing thrombotic risk in susceptible individuals
Influences hepatic protein synthesis including binding globulins and clotting factors
Reduces ovarian follicular development and steroidogenesis
Decreases gonadotropin secretion via negative feedback on hypothalamic-pituitary axis
Iron supplementation through ferrous fumarate tablets aids in preventing iron deficiency during menstruation
Maintains menstrual cycle regularity with scheduled withdrawal bleeding
Modulates CNS pathways impacting mood and neurological symptoms
Exerts anti-estrogenic effects on certain target tissues due to progestin action
Potential to influence bone metabolism through estrogenic activity

Therapeutic Or Clinical Uses

Prevention of pregnancy in women of reproductive age
Oral contraceptive therapy for regular menstrual cycle management
Treatment to reduce menstrual blood loss and supplementation of iron via ferrous fumarate
Management of dysmenorrhea associated with ovulatory cycles
Use as a contraceptive option for women requiring a low-dose estrogen/progestin formulation
Suitable for use in adolescents and adults with established menses
Contraceptive choice for women who prefer oral administration and scheduled withdrawal bleeding
Use in women without contraindications to combined oral contraceptives
May be considered in women without histories of thromboembolic events or uncontrolled hypertension
Available for cycle control in women switching from other contraceptive methods
Use in women requiring reliable contraception while managing mild iron deficiency anemia from menstruation
Option for contraception in women with regulated blood pressure and metabolic profiles
Utility in family planning and pregnancy prevention programs
Alternative contraceptive when non-hormonal methods are unsuitable or declined
Adjunct to counseling on reproductive health and menstrual cycle normalization

Side Or Adverse Effects

Headache, including migraine and increased frequency or severity
Vaginal candidiasis and bacterial vaginitis
Nausea and occasional vomiting
Menstrual cramps and dysmenorrhea
Breast tenderness, pain, or enlargement
Mood changes, including mood swings and depression
Acne exacerbation or new-onset acne
Weight gain in some users
Irregular uterine bleeding, spotting, or breakthrough bleeding especially in initial months
Thromboembolic events including deep vein thrombosis, pulmonary embolism, and arterial thrombosis
Hypertension or elevation of blood pressure
Elevated liver enzymes and rare hepatic adenomas or tumors
Gallbladder disease including cholestasis and gallstones
Visual disturbances including blurred vision or retinal vascular thrombosis
Allergic reactions including rash, pruritus, angioedema, and anaphylactic reactions
Changes in libido including decreased sexual desire
Gastrointestinal disturbances such as abdominal pain and pancreatitis
Rare neurological adverse effects such as dizziness, somnolence, or loss of consciousness
Potential increased risk of hormone-sensitive malignancies such as breast and cervical cancer

Precautions

Avoid use in women over 35 years who smoke due to increased cardiovascular risk
Monitor blood pressure regularly in women with hypertension or cardiovascular risk factors
Use with caution or avoid in women with history or risk of thrombotic or thromboembolic disorders
Evaluate any new, persistent, or severe headaches especially with focal neurological signs
Assess for liver function abnormalities and discontinue if jaundice develops
Monitor glucose tolerance in diabetic or prediabetic patients
Consider alternative contraception for women with uncontrolled dyslipidemia
Advise against use in women with known or suspected breast cancer
Screen and evaluate unexplained vaginal bleeding before initiating therapy
Exercise caution when co-administered with CYP3A4 enzyme inducers that may reduce contraceptive efficacy
Counsel breastfeeding women that Junel Fe 24 may reduce milk production
Be aware of the potential for mood alterations; monitor patients with a history of depression
Instruct patients on proper adherence to dosing to minimize breakthrough bleeding and pregnancy risk
Recommend avoidance of sunlight or UV exposure if predisposed to chloasma
Discontinue use prior to major surgery or prolonged immobilization to mitigate VTE risk

Warnings

Black Box Warning: Cigarette smoking in women over 35 years significantly increases risk of serious cardiovascular events including myocardial infarction, stroke, and death
Increased risk of venous thromboembolism (VTE) especially during first year of use or after treatment interruption
Risk of arterial thromboses including cerebrovascular accidents and myocardial infarction heightened in presence of cardiovascular risk factors
Use contraindicated in women with current or history of thrombotic events or known thrombogenic disorders
Contraindicated in women with benign or malignant liver tumors or active liver disease
Patients should discontinue Junel Fe 24 if unexplained visual loss or retinal vascular thrombosis symptoms occur
Discontinue during pregnancy as contraception is not indicated and no benefit demonstrated
Potential for elevated liver enzymes when co-administered with certain hepatitis C treatments; contraindicated with ombitasvir/paritaprevir/ritonavir ± dasabuvir
Careful consideration warranted in women with a history of migraine with aura, especially if over 35 years old
Potential for increased blood pressure; monitor regularly and discontinue if severe hypertension develops
May cause serious allergic reactions including angioedema, which can be life-threatening
Use in women with history of depression requires monitoring for exacerbation of symptoms
Possible association with increased risk of hormone-sensitive breast and cervical cancers
May cause gallbladder disease or exacerbate pre-existing conditions
COCs may interfere with certain laboratory tests; inform laboratory personnel of use

Contraindication

Women over 35 years who smoke cigarettes
Current or past history of arterial or venous thrombotic disease, including deep vein thrombosis, pulmonary embolism, cerebrovascular disease, and myocardial infarction
Inherited or acquired hypercoagulopathies
Severe or uncontrolled hypertension
Diabetes mellitus with vascular disease
Headaches with focal neurological symptoms or migraine with aura; any migraine in women over 35 years
Known or suspected breast cancer or other estrogen- or progestin-sensitive malignancies
Benign or malignant liver tumors or acute or chronic liver disease
Undiagnosed abnormal vaginal bleeding
Concomitant use with Hepatitis C drug combinations containing ombitasvir/paritaprevir/ritonavir with or without dasabuvir due to risk of severe liver enzyme elevations
Known hypersensitivity to any component of Junel Fe 24
Pregnancy — not indicated and should be discontinued if pregnancy is confirmed
Women with thrombogenic valvular or thrombogenic rhythm heart diseases
Past history of cholestasis related to pregnancy or prior hormonal contraceptive use

Drug Interactions

Enzyme inducers such as phenytoin, carbamazepine, barbiturates, rifampicin, rifabutin, griseofulvin, topiramate, oxcarbazepine, and products containing St. John's wort may reduce efficacy by decreasing plasma concentrations, increasing risk of breakthrough bleeding and pregnancy
CYP3A4 inhibitors like itraconazole, ketoconazole, fluconazole, voriconazole, and grapefruit juice may increase plasma levels of contraceptive hormones
Protease inhibitors and non-nucleoside reverse transcriptase inhibitors used in HIV/HCV therapy may alter plasma concentrations of estrogens and progestins unpredictably
Co-administration with atorvastatin or rosuvastatin can increase ethinyl estradiol exposure by 20-25%
Acetaminophen and ascorbic acid may increase ethinyl estradiol plasma concentrations via conjugation inhibition
Contraceptives may increase plasma concentrations of cyclosporine, prednisolone, theophylline, tizanidine, and voriconazole due to metabolic inhibition
Contraceptives may decrease plasma concentrations and efficacy of lamotrigine through induction of glucuronidation requiring dosage adjustment
Women on thyroid hormone replacement may need higher doses due to increased thyroxine-binding globulin induced by estrogen
COCs can decrease plasma concentrations of acetaminophen, clofibric acid, morphine, salicylic acid, and temazepam, potentially altering therapeutic effects
Coadministration with HCV drugs containing ombitasvir/paritaprevir/ritonavir with or without dasabuvir is contraindicated due to risk of severe ALT elevations
Coadministration with glecaprevir/pibrentasvir is not recommended for similar reasons
Potential interactions may alter results of laboratory tests including coagulation factors, lipids, glucose tolerance, and binding proteins
Use backup contraception when enzyme inducers are used and continue backup for 28 days post-discontinuation of inducers

Preparations Of The Drug

Blister packs containing 28 oral tablets: 24 active light yellow tablets with 1 mg norethindrone acetate and 0.02 mg ethinyl estradiol each
4 inert brown tablets containing 75 mg ferrous fumarate serving as iron supplement and hormone-free reminder tablets
Active tablets round, flat-faced, beveled-edge, approximately 6 mm in diameter, debossed with 'b' and '977'
Inert tablets round, flat-faced, beveled-edge, approximately 6 mm in diameter, debossed with 'b' and '247'
Packaged in cartons containing three blister cards of 28 tablets each for retail distribution
Non-hormonal ferrous fumarate tablets do not meet USP standards for dissolution and assay
Inactive ingredients in active tablets include acacia, compressible sugar, D&C yellow no. 10 aluminum lake, lactose monohydrate, magnesium stearate, and pregelatinized corn starch
Inactive ingredients in inert tablets include crospovidone, hydrogenated cottonseed oil, and microcrystalline cellulose
Storage conditions recommend protection from light and maintenance at controlled room temperature between 20° to 25°C (68° to 77°F)
Each package includes a detailed patient information leaflet and instructions for use to ensure adherence and safety