NORINYL
Clinical safety rating
cautionComprehensive clinical and safety monograph for NORINYL (NORINYL).
Combination of norethindrone (progestin) and ethinyl estradiol (estrogen) provides contraception by inhibiting gonadotropin secretion via negative feedback on the hypothalamic-pituitary-ovarian axis, suppressing ovulation, increasing cervical mucus viscosity, and altering endometrial receptivity.
| Metabolism | Norethindrone is metabolized primarily via reduction and conjugation; ethinyl estradiol is metabolized via CYP3A4 and undergoes glucuronidation. Both undergo enterohepatic circulation. |
| Excretion | Renal: ~60% as metabolites, biliary/fecal: ~40% as glucuronide conjugates |
| Half-life | Terminal half-life: norethindrone 7-8 hours, ethinyl estradiol 13-27 hours; clinical context: steady-state achieved in 3-5 half-lives |
| Protein binding | Norethindrone: 80% bound to albumin and SHBG; ethinyl estradiol: 97% bound to albumin |
| Volume of Distribution | Norethindrone: 4 L/kg, indicates extensive tissue distribution; ethinyl estradiol: 4-5 L/kg |
| Bioavailability | Oral: norethindrone ~65%, ethinyl estradiol ~40-45% due to first-pass metabolism |
| Onset of Action | Oral: contraceptive effect begins after 7 days of continuous dosing |
| Duration of Action | 24 hours; one tablet daily maintains contraceptive effect |
| Molecular Weight | 310.48 |
One tablet (norethindrone 1 mg/ethinyl estradiol 0.035 mg) orally once daily for 21 days, followed by 7 placebo tablets. For first cycle, start on first Sunday after menstruation begins or on day 1 of menstrual cycle.
| Dosage form | TABLET |
| Renal impairment | No specific GFR-based dose adjustments recommended; use with caution in renal impairment due to potential fluid retention. |
| Liver impairment | Contraindicated in Child-Pugh class B or C (severe hepatic impairment) or active liver disease. For mild impairment (Child-Pugh A), use with caution and monitor liver function. |
| Pediatric use | Not indicated for use before menarche; dosing for postmenarchal adolescents same as adult. |
| Geriatric use | Not indicated for use in postmenopausal women; no geriatric dosing established due to lack of indication. |
| 1st trimester | Contraindicated due to risk of birth defects; nonsteroidal estrogen-progestin combinations should not be used during pregnancy. |
| 2nd trimester | Contraindicated as pregnancy must be excluded before use; no indication for use during pregnancy. |
| 3rd trimester | Contraindicated due to potential adverse effects on fetal development and pregnancy outcome. |
Clinical note
Comprehensive clinical and safety monograph for NORINYL (NORINYL).
| Placental transfer | Estrogen and progestin components readily cross the placenta; degree of transfer is significant based on lipophilicity and molecular size. |
| Breastfeeding | Excreted in small amounts into breast milk; may reduce milk production and quality. Use only if clearly needed and with caution, monitoring infant for jaundice and signs of estrogen exposure. |
| Lactation Rating | L3 (Moderately Safe; potential for moderate adverse effects or excretion in significant amounts) |
| Teratogenic Risk | Pregnancy category X. Contraindicated in pregnancy. First trimester: Increased risk of congenital anomalies, including cardiac and limb defects, due to progestin and estrogen exposure. Second and third trimesters: Risk of feminization of male fetus, urogenital sinus abnormalities, and clitoral hypertrophy from progestin (norethindrone). Post-fertilization: Disruption of fetal development. |
| Fetal Monitoring | If inadvertent exposure during pregnancy, monitor fetal growth and development via ultrasound. Maternal monitoring includes blood pressure, liver function, and signs of thromboembolism. No routine fetal monitoring required unless complications arise. |
| Fertility Effects | Suppresses ovulation via inhibition of gonadotropins. Normal fertility typically returns within 1-3 cycles after discontinuation. No permanent adverse effects on fertility. |
■ FDA Black Box Warning
Cigarette smoking increases the risk of serious cardiovascular events from combination oral contraceptives. This risk increases with age and heavy smoking (≥15 cigarettes/day) and is significant in women over 35. Women over 35 who smoke should not use this product.
| Serious Effects |
Known or suspected pregnancyUndiagnosed abnormal genital bleedingKnown or suspected carcinoma of the breastKnown or suspected estrogen-dependent neoplasiaActive hepatic disease or impaired liver functionHistory of thrombophlebitis, thromboembolic disorders, or cerebrovascular accidentCurrent or past history of breast cancer (for combined estrogen-progestin products)
| Precautions | Thrombotic disorders (venous thromboembolism, arterial thromboembolism, stroke, myocardial infarction), Cerebrovascular disease, Hepatic neoplasia (benign and malignant), Gallbladder disease, Hypertension, Carbohydrate and lipid metabolism effects, Ocular lesions (retinal thrombosis, optic neuritis), Headache (including migraine), Breakthrough bleeding and spotting, Depression, Malignant neoplasms (breast, cervical), Effect on pregnancies (fetal harm if used during pregnancy), Lactation (may decrease milk production), Hereditary angioedema, Chloasma, Laboratory test interference |
| Food/Dietary | Avoid grapefruit juice as it may alter metabolism; no other significant food interactions reported. |
| Clinical Pearls | Monitor for thromboembolic events, especially in smokers over 35. Use as part of a combined oral contraceptive regimen; may cause breakthrough bleeding. Check for drug interactions with rifampin, carbamazepine, and certain antibiotics. |
| Patient Advice | Take at the same time daily to maintain consistent hormone levels. · Report signs of blood clots (leg pain, chest pain, sudden headache) immediately. · Use backup contraception if you miss a dose or start a new medication. · Do not smoke while taking this medication, especially if over 35 years old. · This medication does not protect against sexually transmitted diseases. |
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