NORINYL 1+50 21-DAY
Clinical safety rating
cautionComprehensive clinical and safety monograph for NORINYL 1+50 21-DAY (NORINYL 1+50 21-DAY).
Norinyl 1+50 21-Day contains norethindrone (a progestin) and mestranol (an estrogen). Mestranol is converted to ethinyl estradiol, which provides negative feedback on gonadotropin release, inhibiting ovulation. Norethindrone suppresses gonadotropins and alters cervical mucus and endometrial lining to prevent implantation.
| Metabolism | Mestranol is demethylated to ethinyl estradiol; ethinyl estradiol and norethindrone are metabolized by CYP3A4. Conjugation (glucuronidation and sulfation) occurs in the liver and gut wall. |
| Excretion | Renal (40% as metabolites), fecal (50% as metabolites), <1% unchanged |
| Half-life | Norethindrone: 5-8 hours; Ethinyl estradiol: 7-15 hours; steady-state reached within 5-7 days |
| Protein binding | Norethindrone: ~80% bound to SHBG and albumin; Ethinyl estradiol: ~97% bound to albumin, 2-3% free |
| Volume of Distribution | Norethindrone: Vd approximately 4 L/kg; Ethinyl estradiol: Vd approximately 2.5 L/kg; indicates extensive tissue distribution |
| Bioavailability | Oral: Norethindrone ~90%; Ethinyl estradiol ~97-98% (due to low first-pass metabolism) |
| Onset of Action | Oral: Onset of contraceptive effect within 5-7 days if started on day 1 of menstrual cycle; immediate if started on first day of menses |
| Duration of Action | Contraceptive protection lasts 21 days of active pills; pill-free interval of 7 days allows withdrawal bleed; duration of effect is 24 hours per active dose |
| Molecular Weight | Norethindrone: 298.42 Da; Ethinyl estradiol: 296.40 Da. Combined product: not applicable. |
One tablet (1 mg norethindrone + 0.05 mg mestranol) orally once daily for 21 days, followed by 7 placebo tablets. Start on day 1 of menstrual cycle or first Sunday after onset.
| Dosage form | TABLET |
| Renal impairment | No dosage adjustment required for mild-to-moderate renal impairment. Contraindicated in severe renal impairment (GFR <30 mL/min) due to risk of fluid retention and hyperkalemia. |
| Liver impairment | Contraindicated in acute hepatitis, severe cirrhosis (Child-Pugh class C), or liver tumors. Dose adjustment not recommended for mild hepatic impairment (Child-Pugh A) but use with caution; avoid in moderate-to-severe impairment (Child-Pugh B or C). |
| Pediatric use | Not indicated in pediatric females before menarche. For postmenarchal adolescents, dose same as adults: one tablet orally once daily for 21 days. |
| Geriatric use | Not indicated in postmenopausal women due to lack of efficacy and increased risk of thromboembolic events, cardiovascular disease, and malignancy. |
| 1st trimester | Use is contraindicated in pregnancy. Norethindrone and ethinyl estradiol are associated with teratogenic risk and should not be used during the first trimester. |
| 2nd trimester | Contraindicated in pregnancy due to risk of fetal harm during organogenesis. |
| 3rd trimester | Contraindicated in pregnancy; may cause fetal androgenization and other adverse effects. |
Clinical note
Comprehensive clinical and safety monograph for NORINYL 1+50 21-DAY (NORINYL 1+50 21-DAY).
| Placental transfer | Norethindrone and ethinyl estradiol cross the placenta; evidence includes detection in fetal tissues and association with adverse outcomes. |
| Breastfeeding | Norethindrone and ethinyl estradiol are excreted in breast milk in low amounts. Use is generally not recommended during breastfeeding as it may reduce milk production and affect the infant. Alternative contraception should be considered. |
| Lactation Rating | L3 (Moderately Safe) - Limited data suggest low risk but alternative agents are preferred. |
| Teratogenic Risk | FDA Pregnancy Category X. First trimester: Use is contraindicated due to increased risk of congenital anomalies, particularly cardiovascular and limb defects. Second and third trimesters: Associated with masculinization of female fetuses (pseudohermaphroditism) due to androgenic activity of norethindrone. Estrogen component may cause fetal harm. Discontinue immediately if pregnancy occurs. |
| Fetal Monitoring | Monitor blood pressure (risk of hypertension), liver function tests (risk of cholestatic jaundice), and blood glucose (risk of glucose intolerance). Evaluate for signs of thrombosis (especially if prolonged use). In case of exposure during pregnancy, monitor fetal development with ultrasound for congenital anomalies. |
| Fertility Effects | No known permanent effects on fertility. Upon discontinuation, ovulation typically resumes within 1-3 months. There is no evidence of irreversible impairment. Do not use for pregnancy detection or for fertility indication. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular side effects from combined oral contraceptives. Risk increases with age (especially >35 years) and with heavy smoking (≥15 cigarettes/day). Women should not use combined oral contraceptives if they smoke and are over 35 years old.
| Serious Effects |
Known or suspected pregnancyThrombophlebitis or thromboembolic disordersHistory of deep vein thrombosis or pulmonary embolismCerebrovascular or coronary artery diseaseValvular heart disease with complicationsSevere hypertensionDiabetes with vascular involvementHeadaches with focal neurological symptomsMajor surgery with prolonged immobilizationKnown or suspected carcinoma of the breast or endometriumUndiagnosed abnormal genital bleedingCholestatic jaundice of pregnancy or jaundice with prior pill useHepatic adenoma or carcinomaKnown hypersensitivity to norethindrone or ethinyl estradiol
| Precautions | Thrombotic disorders (thrombophlebitis, pulmonary embolism, cerebral hemorrhage, myocardial infarction), Carcinoma of reproductive organs (breast, endometrium), Hepatic adenoma or liver tumors, Elevated blood pressure, Gallbladder disease, Carbohydrate and lipid metabolism effects, Bleeding irregularities (breakthrough bleeding, amenorrhea), Ocular lesions (optic neuritis, retinal thrombosis), Possible migraine exacerbation |
| Food/Dietary | Grapefruit juice may inhibit CYP3A4 metabolism, increasing ethinyl estradiol levels and potential adverse effects (nausea, breast tenderness, thromboembolism). St. John's Wort may decrease contraceptive efficacy. No significant interactions with other foods. |
| Clinical Pearls | For combination oral contraceptives (COCs) like NORINYL 1+50, counsel patients that concurrent use of CYP3A4 inducers (e.g., rifampin, certain anticonvulsants) may reduce contraceptive efficacy. Advise backup contraception or alternate method. Norethindrone 1 mg/ethinyl estradiol 50 mcg has higher estrogen content; consider increased thromboembolism risk vs low-dose pills. Monitor for hypertension, migraine with aura, and breakthrough bleeding patterns. |
| Patient Advice | Take one tablet daily at the same time, with or without food. Follow pack directions: 21 active pills then 7 placebo days. · Expect withdrawal bleeding during placebo week; if no bleed occurs, consider pregnancy test. · Missed pill: if delayed <12 hours, take immediately; if >12 hours, take last missed pill and use backup contraception for 7 days. · Common side effects: nausea, breast tenderness, headache; usually improve within 3 months. · Report severe leg pain/chest pain/sudden dyspnea/speech changes as possible signs of blood clot. · Avoid grapefruit juice as it may increase estrogen levels and side effects. · Does not protect against STIs; use condoms for prevention. |
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