NORINYL 1+35 21-DAY
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NORINYL 1+35 21-DAY (NORINYL 1+35 21-DAY).
Combination oral contraceptive containing norethindrone (progestin) and ethinyl estradiol (estrogen). Suppresses gonadotropin release (FSH, LH) via negative feedback on hypothalamic-pituitary-ovarian axis, inhibiting ovulation. Increases cervical mucus viscosity and alters endometrial structure to impair sperm penetration and implantation.
| Metabolism | Norethindrone: primarily hepatic via reduction, hydroxylation, conjugation (glucuronidation); CYP3A4 contributes to minor extent. Ethinyl estradiol: hepatic via CYP3A4 hydroxylation, glucuronidation, and sulfation; undergoes enterohepatic recirculation. |
| Excretion | Renal (50-60% as metabolites, primarily glucuronide and sulfate conjugates) and fecal (30-40% as metabolites). Less than 1% excreted unchanged. |
| Half-life | Norethindrone: 7-8 hours; Ethinyl estradiol: 13-27 hours (mean ~17 hours). Steady state achieved by day 10-14. |
| Protein binding | Norethindrone: 61% bound to albumin and 36% to SHBG; Ethinyl estradiol: 98% bound to albumin. |
| Volume of Distribution | Norethindrone: 2-4 L/kg; Ethinyl estradiol: 2-4 L/kg. Indicates extensive tissue distribution. |
| Bioavailability | Oral: Norethindrone 64% (first-pass metabolism); Ethinyl estradiol 40-45% (first-pass metabolism). |
| Onset of Action | Oral: 7 days of continuous dosing required for full contraceptive effect (inhibition of ovulation). |
| Duration of Action | 24 hours; requires daily dosing. Missed doses increase pregnancy risk. |
One tablet orally once daily for 21 consecutive days, followed by 7 days off therapy.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment recommended; use with caution in patients with renal impairment. |
| Liver impairment | Contraindicated in patients with severe hepatic disease (Child-Pugh class C); use with caution in mild to moderate impairment (Child-Pugh A or B), with monitoring of liver function. |
| Pediatric use | Not indicated for use in pediatric patients before menarche; after menarche, standard adult dosing applies. |
| Geriatric use | Not indicated for use in postmenopausal women; no specific dosing adjustments for elderly patients otherwise. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NORINYL 1+35 21-DAY (NORINYL 1+35 21-DAY).
| Breastfeeding | Excreted into breast milk in small amounts. Norethindrone: M/P ratio approximately 0.5 (for 1 mg doses; ratio for 1 mg norethindrone + 35 mcg ethinyl estradiol not specifically reported but likely similar). Estrogen component may reduce milk quantity and quality. Use not recommended during breastfeeding due to potential adverse effects on infant and lactation, especially in first 6 weeks postpartum. Low-dose progestin-only contraceptives are preferred. |
| Teratogenic Risk | Pregnancy category X. Contraindicated in pregnancy. First trimester: increased risk of congenital anomalies including neural tube defects, cardiovascular defects, and limb reduction defects (based on epidemiological studies with combined hormonal contraceptives). Second and third trimesters: no direct fetal risk from continued use post-organogenesis, but due to lack of indication and potential risks such as fetal harm from progestins (androgenicity), use is contraindicated. Immediate discontinuation recommended if pregnancy occurs. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular events (thrombosis, myocardial infarction, stroke) from combination oral contraceptive use. Risk increases with age and number of cigarettes smoked, especially in women over 35 years. Advise not to smoke.
| Serious Effects |
Thrombophlebitis or thromboembolic disorders (current/history). Cerebrovascular or coronary artery disease (current/history). Known/suspected breast carcinoma (current/history). Estrogen-dependent neoplasia. Undiagnosed abnormal genital bleeding. Pregnancy (known/suspected). Hepatic adenoma/carcinoma (current/history). Jaundice or cholestasis with prior OC use. Active liver disease. Hypersensitivity to components. Age >35 and smoking ≥15 cigarettes/day.
| Precautions | Increased risk of thrombotic events (VTE, arterial thrombosis), myocardial infarction, stroke, especially in smokers >35 years. Hepatic neoplasia (benign/malignant). Gallbladder disease. Hypertension. Carbohydrate/lipid effects. Ocular changes (retinal thrombosis). Uterine bleeding irregularities. Depression. Fluid retention. Hereditary angioedema. Chloasma. Impaired glucose tolerance. Lactation suppression. |
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| Fetal Monitoring | Not applicable during pregnancy as drug is contraindicated. In non-pregnant women of childbearing potential: baseline pregnancy test, monitoring for signs of thromboembolism, blood pressure, and hepatic function. If unintentional exposure during pregnancy, fetal ultrasound to assess for anomalies. |
| Fertility Effects | Returns to baseline promptly after discontinuation. No long-term impairment of fertility. No effect on future pregnancy outcomes after cessation. |