NORINYL 1+50 28-DAY
Clinical safety rating: caution
Comprehensive 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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NORINYL 1+50 28-DAY (NORINYL 1+50 28-DAY).
| Breastfeeding | Small amounts of norethindrone and ethinyl estradiol are excreted in breast milk (M/P ratio for norethindrone ~0.6; ethinyl estradiol ~0.1). May reduce milk quantity and quality. Not recommended for breastfeeding mothers; consider alternative contraception. |
| 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. |
■ 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 pregnancy","Current or history of venous thromboembolism","Current or history of arterial thrombotic disease","Uncontrolled hypertension","Diabetes with vascular involvement","Headaches with focal neurological symptoms","Major surgery with prolonged immobilization","Hepatic impairment or active liver disease","Known or suspected breast cancer or other estrogen-sensitive neoplasia","Undiagnosed abnormal uterine bleeding","Cigarette smoking in women >35 years"]
| 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"] |
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| 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. |