MICROGESTIN FE 1/20
Clinical safety rating: caution
Comprehensive 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 |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MICROGESTIN FE 1/20 (MICROGESTIN FE 1/20).
| Breastfeeding | Small amounts of contraceptive steroids and their metabolites are excreted in human milk, with an estimated infant dose of 0.1% to 1% of maternal dose per kg/day. The M/P ratio for norethindrone is approximately 0.6. Breastfeeding safety: use is not recommended while breastfeeding, especially with early postpartum use, due to potential reduction in milk production and content, as well as unknown long-term effects on infant development. Alternative contraception methods should be considered. |
| 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. |
■ 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.
| Serious Effects |
["Thrombophlebitis or thromboembolic disorders (current or history)","Cerebrovascular or coronary artery disease (current or history)","Known or suspected breast carcinoma","Endometrial carcinoma or other estrogen-dependent neoplasia","Undiagnosed abnormal genital bleeding","Cholestatic jaundice of pregnancy or jaundice with prior oral contraceptive use","Hepatic adenoma or carcinoma (current or history)","Known or suspected pregnancy","Heavy smoking (≥15 cigarettes/day) and age >35 years","Uncontrolled hypertension","Diabetes with vascular involvement","Migraine with focal neurological symptoms (current or history)"]
| 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"] |
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| 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. |