NORINYL 1+35 21-DAY
Clinical safety rating
cautionComprehensive 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. |
| Molecular Weight | Norethindrone: 298.42 Da; Ethinyl estradiol: 296.40 Da |
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 | Norethindrone 1 mg/ethinyl estradiol 35 mcg. First trimester exposure: Risk of major malformations (e.g., cardiovascular, limb defects) not increased in most studies, but association with congenital anomalies remains controversial. Use only if benefit outweighs risk. |
| 2nd trimester | Second trimester exposure: Should not be used during pregnancy. Do not use for pregnancy test or to prevent miscarriage. Increased risk of adverse pregnancy outcomes (e.g., gestational diabetes, preeclampsia). |
| 3rd trimester | Third trimester exposure: Avoid. May cause fetal/neonatal adverse effects including jaundice, cholestasis, and potential hormonal effects from sex steroids. Do not use for threatened abortion. |
Clinical note
Comprehensive clinical and safety monograph for NORINYL 1+35 21-DAY (NORINYL 1+35 21-DAY).
| Placental transfer | Significant placental transfer; both components cross the placenta. Norethindrone: 1-2% maternal serum in fetal cord blood. Ethinyl estradiol: crosses but rapidly metabolized by fetal liver. |
| Breastfeeding | Small amounts pass into breast milk (<1% maternal dose). May reduce milk production and quality in the early postpartum period. Use caution, especially in nursing mothers requiring contraception. Consider progestin-only methods if necessary. |
| Lactation Rating | L3 (Moderately Safe) |
| 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. |
| 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. |
■ 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 |
Known or suspected pregnancyCurrent or history of venous thromboembolism (VTE)Major surgery with prolonged immobilizationCurrent or past arterial thromboembolic disease (e.g., stroke, MI)Valvular heart disease with complicationsUncontrolled hypertension (≥160/100 mmHg)Diabetes with vascular involvementSevere headache with focal neurological symptoms (e.g., migraine with aura)Undiagnosed abnormal uterine bleedingKnown or suspected breast cancerBenign or malignant liver tumor (active or history)Acute liver disease or decompensated cirrhosisCigarette smoking in women ≥35 years oldCo-administration with certain antiviral (Hepatitis C) or antiepileptic drugs (e.g., ombitasvir/paritaprevir/ritonavir, phenytoin)
| 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. |
| Food/Dietary | Grapefruit and grapefruit juice may increase estrogen levels; avoid excessive consumption. |
| Clinical Pearls | Monitor for breakthrough bleeding, which is common in first 3 cycles. Advise use of backup contraception if vomiting within 2 hours of dose. Check blood pressure at baseline and follow-up due to estrogen component. |
| Patient Advice | Take one tablet daily at the same time each day for 21 consecutive days, then none for 7 days. · If you miss a dose, take it as soon as remembered and use backup contraception for 7 days. · Smoking increases risk of serious cardiovascular side effects; avoid smoking. · Notify your healthcare provider if you experience severe headaches, vision changes, or leg pain/swelling. |
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