MICROGESTIN FE 1/20
Clinical safety rating
cautionComprehensive clinical and safety monograph for MICROGESTIN FE 1/20 (MICROGESTIN FE 1/20).
Combination oral contraceptive containing ethinyl estradiol (estrogen) and norethindrone acetate (progestin). Suppresses gonadotropins via negative feedback on hypothalamic-pituitary axis, inhibiting ovulation; increases cervical mucus viscosity and alters endometrial lining.
| Metabolism | Primarily hepatic via CYP3A4. Norethindrone acetate undergoes reduction and conjugation; ethinyl estradiol is metabolized by CYP3A4 and undergoes glucuronidation. |
| Excretion | Renal: ~50-60% as metabolites; Fecal: ~30-40% as metabolites; Biliary: minor; <1% unchanged |
| Half-life | Norethindrone: 5-14 hours (mean 8 hours); Ethinyl estradiol: 12-24 hours (mean 18 hours); Steady-state in 5-7 days |
| Protein binding | Norethindrone: 61% to albumin, 36% to SHBG; Ethinyl estradiol: 98% to albumin |
| Volume of Distribution | Norethindrone: 2.1 L/kg; Ethinyl estradiol: 2.8 L/kg |
| Bioavailability | Oral: Norethindrone ~65%; Ethinyl estradiol ~40-45% |
| Onset of Action | Oral: 7 days of continuous dosing for contraceptive effect; Immediate for hormone regulation |
| Duration of Action | 24 hours (once-daily dosing); Withdrawal bleed within 2-3 days after active tablets |
| Molecular Weight | 340.46 |
| Action Class | Oral Contraceptive; Estrogen/Progestin Combination |
One tablet orally once daily, containing norethindrone acetate 1 mg and ethinyl estradiol 20 mcg, taken at the same time each day for 21 days followed by 7 days of placebo (iron tablets) or continuous cycling per prescribing information.
| Dosage form | TABLET |
| Renal impairment | No dosage adjustment required for mild to moderate renal impairment. Not studied in severe renal impairment (GFR <30 mL/min) or end-stage renal disease; use caution due to potential for estrogen accumulation and metabolic effects. |
| Liver impairment | Contraindicated in Child-Pugh Class C (severe hepatic impairment). For Child-Pugh Class A or B, use only if benefits outweigh risks; monitor for adverse effects; consider alternative contraception due to altered hormone metabolism. |
| Pediatric use | Post-menarchal pediatric patients: Same dosing as adults. Safety and efficacy established in adolescents; use according to standard adult regimen. |
| Geriatric use | Not indicated for postmenopausal women; no specific dosing recommendations. Use caution in elderly if prescribed off-label due to increased risk of thromboembolic events, cardiovascular disease, and malignancy. |
| 1st trimester | Contraindicated due to estrogen component; increased risk of congenital anomalies (e.g., cardiovascular defects, limb reduction defects) and VACTERL association. Not recommended for use during pregnancy. |
| 2nd trimester | Contraindicated due to estrogen component; may cause fetal harm. Should not be used during pregnancy. Risk of masculinization of female fetus with progestins. |
| 3rd trimester | Contraindicated due to estrogen component; may cause fetal harm. Should not be used during pregnancy. Potential for withdrawal bleeding and hormonal effects. |
Clinical note
Comprehensive clinical and safety monograph for MICROGESTIN FE 1/20 (MICROGESTIN FE 1/20).
| Placental transfer | Estrogens and progestins cross the placenta. Norethindrone acetate and ethinyl estradiol are detectable in fetal tissue and cord blood. Degree: High (significant transfer). |
| Breastfeeding | Small amounts of estrogen and progestin pass into breast milk. May reduce milk production and quality. Use alternative contraception unless benefit outweighs risk. Generally not recommended during breastfeeding. |
| Lactation Rating | L3 (Moderately Safe) - limited data; potential for adverse effects on infant development and milk supply. |
| Teratogenic Risk | FDA Pregnancy Category X. Estrogens and progestins are contraindicated in pregnancy due to risk of fetal harm. Epidemiological studies have not revealed an increased risk of birth defects in women who inadvertently used combined oral contraceptives during early pregnancy. However, use of progestins alone during the first trimester of pregnancy is associated with genital abnormalities in female fetuses, including hypospadias and mild clitoral hypertrophy. Post-fertilization effects: no evidence of increased risk of spontaneous abortion or low birth weight with inadvertent use during early pregnancy. Second and third trimesters: no therapeutic indication; potential for estrogenic effects on fetal development, but data are limited due to contraindication. |
| Fetal Monitoring | Because MICROGESTIN FE 1/20 is contraindicated in pregnancy, no routine monitoring for fetal effects is indicated. However, if inadvertent exposure occurs in early pregnancy, standard prenatal care includes ultrasound for fetal anatomy assessment. Maternal monitoring: no specific monitoring required for pregnancy-related complications, as drug should be discontinued immediately upon pregnancy confirmation. |
| Fertility Effects | Reversible inhibition of ovulation via gonadotropin suppression. Use of combination oral contraceptives does not impair future fertility. Return to normal ovulatory cycles may occur within 1–2 months after discontinuation. No permanent effects on fertility. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular events from combination oral contraceptive use. Risk increases with age (especially >35 years) and with heavy smoking (≥15 cigarettes/day). Women who use combination oral contraceptives should be strongly advised not to smoke.
| Common Effects | Nausea, Headache, Breast tenderness, Weight changes, Irregular uterine bleeding, Mood changes, Acne |
| Serious Effects | Venous thromboembolism (VTE), Arterial thromboembolism (e.g., stroke, myocardial infarction), Hepatic adenoma or hepatocellular carcinoma, Hypertension, Gallbladder disease, Thrombotic thrombocytopenic purpura (TTP), Hemolytic uremic syndrome (HUS) |
Pregnancy or suspected pregnancyBreast cancer (current or history)Undiagnosed abnormal genital bleedingThromboembolic disorders (current or history)Active liver disease or impaired liver functionKnown or suspected estrogen-dependent neoplasiaHypersensitivity to any componentSmoking over age 35 (>15 cigarettes/day)
| Precautions | Increased risk of thromboembolic disorders (e.g., stroke, MI, VTE), especially in smokers and women with hypertension, diabetes, or hyperlipidemias, Elevated risk of cervical and breast cancer, Hepatic neoplasia (benign and malignant), Gallbladder disease, Carbohydrate and lipid metabolism alterations, Hypertension, Headache/migraine, Irregular bleeding, Depression, Contact lens intolerance, Possible decreased efficacy with hepatic enzyme inducers, Discontinue if jaundice, visual disturbances, or thromboembolic symptoms occur |
| Food/Dietary | No specific food restrictions. Grapefruit juice may modestly increase estrogen levels but is not contraindicated. High-fat meals may increase estrogen absorption. Calcium-rich foods or supplements may reduce iron absorption from placebo tablets; separate intake by several hours. |
| Clinical Pearls | Contains norethindrone acetate 1 mg and ethinyl estradiol 20 mcg with ferrous fumarate 75 mg as placebo tablets. Iron supplementation may improve hematologic parameters in anemic patients. Bleeding irregularities are common in first 3-6 months; counsel on adherence to prevent breakthrough bleeding. Caution in patients with migraine with aura, history of VTE, or smokers over 35. CYP3A4 inducers like rifampin may reduce efficacy; consider alternative contraception. |
| Patient Advice | Take one tablet daily at the same time each day, preferably with food to reduce nausea. · The last 7 tablets (brown) contain iron and are inactive; continue taking them to maintain the habit. · Bleeding may be irregular initially; report heavy or prolonged bleeding to your healthcare provider. · Do not smoke while taking this medication, especially if over 35, as it increases clot risk. · Use additional non-hormonal contraception (e.g., condoms) if you miss a pill or have vomiting/diarrhea. · Store at room temperature away from moisture and heat. |
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