NORINYL 1+50 28-DAY
Clinical safety rating
cautionComprehensive clinical and safety monograph for NORINYL 1+50 28-DAY (NORINYL 1+50 28-DAY).
Norethindrone and ethinyl estradiol combination works by suppressing gonadotropin-releasing hormone (GnRH) from the hypothalamus, reducing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion, thereby inhibiting ovulation. Norethindrone also alters cervical mucus viscosity and endometrial lining, impeding sperm penetration and implantation.
| Metabolism | Norethindrone is primarily metabolized via reduction to dihydro metabolites and glucuronide conjugation, with minor involvement of CYP3A4. Ethinyl estradiol is primarily metabolized by CYP3A4, with extensive first-pass metabolism and conjugation (sulfation and glucuronidation). |
| Excretion | Renal: ~40% as metabolites; Biliary/Fecal: ~60% as metabolites. |
| Half-life | Norethindrone: ~8-11 hours; Mestranol: 24 hours (prodrug, ethinyl estradiol half-life ~13-27 hours). |
| Protein binding | Norethindrone: ~80% bound to albumin and SHBG; Ethinyl estradiol: ~97% bound to albumin. |
| Volume of Distribution | Norethindrone: ~4 L/kg; Ethinyl estradiol: ~15 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: Norethindrone ~64%; Ethinyl estradiol ~40-50% (due to first-pass metabolism). |
| Onset of Action | Oral: Contraceptive effect begins after 7 days of continuous use if started on day 1 of menstrual cycle. |
| Duration of Action | Contraceptive protection lasts for each 28-day cycle; withdrawal bleeding occurs during placebo week. |
| Molecular Weight | 340.45 |
One tablet orally once daily for 28 days, with 7 inactive tablets during the last 7 days. Each active tablet contains norethindrone 1 mg and ethinyl estradiol 50 mcg.
| Dosage form | TABLET |
| Renal impairment | No dosage adjustment is required for mild to moderate renal impairment. Use is contraindicated in patients with end-stage renal disease or on dialysis due to potential fluid retention and hypertension. |
| Liver impairment | Contraindicated in patients with acute hepatitis, hepatic cirrhosis, or liver tumors (benign or malignant). For Child-Pugh Class A, use with caution; Class B or C: contraindicated due to impaired metabolism and risk of cholestasis. |
| Pediatric use | Not indicated for use before menarche. For post-menarchal adolescents, dosing is the same as adults (one tablet daily). Safety and efficacy have not been established in prepubertal children. |
| Geriatric use | Not indicated for use in postmenopausal women due to lack of efficacy and increased cardiovascular risks. If used off-label, monitor for thromboembolism, hypertension, and hepatic effects. |
| 1st trimester | Avoid use; may cause fetal harm. Risk of congenital anomalies including cardiovascular and neural tube defects, especially with first-trimester exposure. |
| 2nd trimester | Avoid use; may cause fetal harm. Potential for fetotoxicity including reduced fetal weight and developmental toxicity. |
| 3rd trimester | Avoid use; may cause fetal harm. Risk of neonatal withdrawal, respiratory depression, and other adverse effects. |
Clinical note
Comprehensive clinical and safety monograph for NORINYL 1+50 28-DAY (NORINYL 1+50 28-DAY).
| Placental transfer | Norethindrone crosses the placenta; based on progestin pharmacology, placental transfer is expected. Animal studies indicate fetal exposure, but human data are limited. |
| Breastfeeding | Norethindrone is excreted in breast milk in small amounts; however, limited data suggest no significant adverse effects on infant growth or development. Caution is advised, especially in the first postpartum month, due to potential impact on milk production and infant hormonal balance. Monitor infant for jaundice, drowsiness, and feeding difficulties. |
| Lactation Rating | L2 (Limited data - possibly compatible) |
| Teratogenic Risk | Contraindicated in pregnancy. Category X: Use in first trimester has been associated with congenital defects including cardiovascular and limb defects. Exposure in second and third trimesters may cause fetal harm including masculinization of female fetuses due to androgenic progestin (norethindrone). Discontinue immediately if pregnancy occurs. |
| Fetal Monitoring | Pregnancy test before initiating therapy. Monitor for signs of pregnancy, breakthrough bleeding, and thromboembolic events during use. If pregnancy suspected, perform β-hCG test. Periodic blood pressure monitoring recommended. |
| Fertility Effects | Suppresses ovulation. Return to normal fertility occurs within 1-2 cycles after discontinuation. No evidence of permanent impairment. Use for emergency contraception may disrupt cycle temporarily. |
■ FDA Black Box Warning
Cigarette smoking increases the risk of serious cardiovascular events from combination oral contraceptives. This risk increases with age, particularly in women over 35 years, and with the number of cigarettes smoked. Women who use combination oral contraceptives should be strongly advised not to smoke.
| Serious Effects |
Known or suspected pregnancyHistory of or current thromboembolic disordersCerebrovascular or coronary artery diseaseUndiagnosed abnormal uterine bleedingKnown or suspected breast carcinomaHepatic adenoma or carcinomaActive liver disease or impaired liver functionHypersensitivity to any component
| Precautions | Increased risk of thromboembolic events, Elevated risk of myocardial infarction and stroke especially in smokers >35, Hepatic neoplasia (benign and malignant) reported, Elevated blood pressure, Gallbladder disease, Carbohydrate and lipid metabolism alterations, Headache including migraine exacerbation, Uterine bleeding irregularities, Possible depression, Reduced efficacy with certain drugs such as enzyme inducers |
| Food/Dietary | No specific food interactions. Grapefruit juice may increase estrogen levels (possible increased risk of side effects); avoid excessive consumption. Maintain consistent diet with regard to vitamin C intake as high doses may enhance estrogen absorption. |
| Clinical Pearls | NORINYL 1+50 28-DAY (norethindrone 1 mg / mestranol 50 mcg) is a first-generation combined oral contraceptive. Monitor for thromboembolic events, especially in smokers over 35. Use with caution in patients with migraine with aura. Breakthrough bleeding may occur; if persistent, rule out pregnancy or consider a pill with higher estrogen or different progestin. Missed pill protocol: if one pill missed, take it as soon as remembered; if two pills missed, take two pills for two days and use backup contraception for 7 days. |
| Patient Advice | Take one pill daily at the same time each day. If you miss a pill, follow the missed pill instructions in the package insert. · Use backup contraception (e.g., condoms) if you miss two or more pills or start a new pack late. · This medication does not protect against sexually transmitted infections (STIs). · Avoid smoking while taking this medication, especially if you are over 35 years old, as it increases the risk of serious cardiovascular side effects. · Inform your healthcare provider if you experience severe headaches, chest pain, leg pain or swelling, vision changes, or jaundice. · If you experience persistent breakthrough bleeding, consult your healthcare provider. · Do not take this medication if you are pregnant or think you may be pregnant. · Store at room temperature away from moisture and heat. |
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