NORLESTRIN FE 1/50
Clinical safety rating
cautionComprehensive clinical and safety monograph for NORLESTRIN FE 1/50 (NORLESTRIN FE 1/50).
Combination of ethinyl estradiol and norethindrone acetate provides negative feedback on gonadotropin release, suppressing ovulation. Also causes cervical mucus thickening and endometrial thinning.
| Metabolism | Norethindrone acetate: extensively metabolized via reduction (to active 5α-dihydro derivatives), hydroxylation, and conjugation; primarily by CYP3A4. Ethinyl estradiol: metabolized by CYP3A4 via hydroxylation and conjugation; undergoes enterohepatic circulation. |
| Excretion | Norethindrone: 20% renal, 80% fecal. Ethinyl estradiol: 40% renal, 60% fecal. |
| Half-life | Norethindrone: 5-12 hours (mean 8 hours). Ethinyl estradiol: 11-16 hours. Clinical context: Steady state reached in 5-7 days. |
| Protein binding | Norethindrone: 97% bound (albumin, SHBG). Ethinyl estradiol: 97% bound (albumin, SHBG, CBG). |
| Volume of Distribution | Norethindrone: 2-4 L/kg; Ethinyl estradiol: 2-4 L/kg; reflects tissue distribution. |
| Bioavailability | Oral: Norethindrone ~64%, Ethinyl estradiol ~38% (first-pass metabolism). |
| Onset of Action | Oral: Onset of contraceptive effect after 7 days of continuous use if started within 5 days of menses; otherwise, 7 days needed. |
| Duration of Action | Oral: 24 hours; missed pill guidelines: if missed >12 hours, consider backup contraception for 7 days. |
| Molecular Weight | 376.5 |
One tablet (norethindrone 1 mg and ethinyl estradiol 50 mcg plus ferrous fumarate 75 mg) orally once daily for 28 days, with 21 active tablets and 7 placebo tablets.
| Dosage form | TABLET |
| Renal impairment | No specific GFR-based dose modifications are recommended. Use with caution in patients with renal impairment or history of renal disease. |
| Liver impairment | Contraindicated in patients with hepatic impairment (Child-Pugh class A, B, or C) due to reduced clearance and risk of adverse effects. |
| Pediatric use | Not indicated in pediatric patients before menarche. In adolescents, dosing is the same as adults (one tablet daily). Safety and efficacy in post-menarcheal adolescents are similar to adults. |
| Geriatric use | Not indicated in geriatric patients. No specific dose adjustment; however, consider age-related risks (e.g., thromboembolism, cardiovascular disease). Use lowest effective dose if necessary. |
| 1st trimester | Contraindicated due to risk of fetal harm; oral contraceptive pills increase risk of congenital anomalies and are not recommended during pregnancy. |
| 2nd trimester | Contraindicated; exposure to sex hormones may cause fetal harm; use only if clearly needed for treatment of specific conditions under specialist guidance. |
| 3rd trimester | Contraindicated; potential adverse effects on fetal development and newborn; avoid use. |
Clinical note
Comprehensive clinical and safety monograph for NORLESTRIN FE 1/50 (NORLESTRIN FE 1/50).
| Placental transfer | Norethindrone and ethinyl estradiol cross the placenta; documented transfer in human studies. |
| Breastfeeding | Excreted in breast milk in small amounts; may reduce milk production and affect infant development. Use is generally not recommended during breastfeeding; consider alternative contraception. |
| Lactation Rating | L4 - Possibly Hazardous |
| Teratogenic Risk | Category X. Not indicated for use during pregnancy. First trimester: No increased risk of birth defects from inadvertent use; however, use is contraindicated. Second and third trimesters: Androgenic steroid exposure may cause feminization of male fetus, genital abnormalities, and potential long-term effects; no safe use established. |
| Fetal Monitoring | Monitor blood pressure, liver function, signs of thromboembolism, and glucose tolerance in women with history of gestational diabetes. Ultrasound for fetal growth and development if inadvertently used during pregnancy. |
| Fertility Effects | Suppresses ovulation via estrogen-progestin combination. Fertility returns after discontinuation. No permanent fertility impairment. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular events (e.g., stroke, myocardial infarction, thromboembolism) from combined hormonal contraceptive use, especially in women over 35 years who smoke.
| Serious Effects |
Known or suspected pregnancyHistory of or current thrombophlebitis or thromboembolic disordersCerebral vascular or coronary artery diseaseKnown or suspected carcinoma of the breastCarcinoma of the endometrium or other estrogen-dependent neoplasiaUndiagnosed abnormal genital bleedingCholestatic jaundice of pregnancy or jaundice with prior pill useHepatic adenoma or carcinomaActive liver disease with abnormal liver function
| Precautions | Thrombotic disorders (DVT, PE, stroke, MI), hepatic neoplasia, gallbladder disease, carbohydrate/lipid effects, hypertension, hereditary angioedema, chloasma, retinal thrombosis (discontinue if sudden vision loss/proptosis/diplopia), depression. |
| Food/Dietary | Grapefruit juice may increase estrogen levels via CYP3A4 inhibition; avoid large quantities. No specific food restrictions, but high-fat meals may delay absorption. Iron absorption is reduced by calcium-rich foods, tea, and coffee; take iron tablets separately from these. |
| Clinical Pearls | Withdrawal bleeding typically occurs during the iron-only tablet phase; absence of bleeding requires pregnancy testing. Iron supplementation in active tablets may cause GI upset. CYP3A4 inducers (e.g., rifampin, carbamazepine) reduce contraceptive efficacy. Venous thromboembolism risk is higher with estrogen-containing pills; avoid in migraine with aura or hypertension. |
| Patient Advice | Take one tablet daily at the same time; the last 7 tablets contain iron, not hormones. · Use backup contraception (e.g., condoms) if you miss a pill, vomit within 2 hours, or have severe diarrhea. · This does not protect against STIs; use condoms for prevention. · Report sudden severe headache, chest pain, leg swelling, or vision changes immediately. · Iron tablets may cause constipation or dark stools; this is normal. |
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