NORINYL 1+50 21-DAY
Clinical safety rating: caution
Comprehensive 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 |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NORINYL 1+50 21-DAY (NORINYL 1+50 21-DAY).
| Breastfeeding | Contraindicated in breastfeeding. Norethindrone and ethinyl estradiol are excreted in breast milk; M/P ratio for norethindrone is approximately 0.5. May reduce milk volume and quality. Known adverse effects include jaundice and breast enlargement in infants. Avoid use during lactation. |
| 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. |
■ 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 |
["Thrombophlebitis or thromboembolic disorders (current or history)","Cerebrovascular or coronary artery disease (current or history)","Known or suspected breast carcinoma","Endometrial carcinoma","Undiagnosed abnormal genital bleeding","Cholestatic jaundice of pregnancy or jaundice with prior pill use","Hepatic adenoma or carcinoma","Known or suspected pregnancy"]
| 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"] |
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| 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. |