NORINYL 1+35 28-DAY
Clinical safety rating
cautionComprehensive clinical and safety monograph for NORINYL 1+35 28-DAY (NORINYL 1+35 28-DAY).
Norethindrone is a progestogen that suppresses gonadotropin release, inhibiting ovulation; ethinyl estradiol is an estrogen that provides negative feedback on the hypothalamic-pituitary-ovarian axis, further suppressing ovulation and altering cervical mucus and endometrial thickness.
| Metabolism | Norethindrone is primarily metabolized via reduction and conjugation; ethinyl estradiol is metabolized by CYP3A4 and undergoes conjugation. Both are hepatically eliminated. |
| Excretion | Renal: 50-60% (conjugates and metabolites), Fecal: 30-40% (biliary elimination of norethindrone and ethinyl estradiol conjugates); total clearance ~4-6 mL/min/kg. |
| Half-life | Norethindrone: 7-8 hours (terminal half-life); steady state achieved after 5 days. Ethinyl estradiol: biphasic with terminal half-life of 13-27 hours (mean ~17 hours). Clinical context: dosing interval of 24 hours allows stable hormone levels after first cycle. |
| Protein binding | Norethindrone: 80-85% bound to albumin and SHBG; Ethinyl estradiol: 95-98% bound to albumin (not strongly to SHBG). |
| Volume of Distribution | Norethindrone: 2-4 L/kg; Ethinyl estradiol: 2.5-5 L/kg; both indicate extensive tissue distribution. |
| Bioavailability | Norethindrone: 64-67% (oral, first-pass metabolism); Ethinyl estradiol: 38-48% (oral, extensive first-pass conjugation); food does not significantly alter bioavailability. |
| Onset of Action | Oral: Contraceptive effect requires 7 days of consecutive dosing to achieve ovulation suppression; therapeutic effect (cycle control) occurs within first cycle (typically 21 days). |
| Duration of Action | 24 hours (supports once-daily dosing); contraceptive efficacy maintained if no missed pills and consistent dosing; after discontinuation, ovulation may return within 1-2 weeks. |
| Molecular Weight | 340.5 |
One tablet orally once daily for 28 consecutive days (21 active tablets followed by 7 inert tablets).
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. Not studied in severe renal impairment (CrCl <30 mL/min); contraindicated in acute renal failure or significant renal disease due to potential fluid retention. |
| Liver impairment | Contraindicated in Child-Pugh class B and C (moderate to severe hepatic impairment). Use with caution in Child-Pugh class A (mild hepatic impairment) as metabolism may be reduced; monitor for adverse effects. |
| Pediatric use | Not indicated for use before menarche. For postmenarchal adolescents, dose is same as adults: one tablet orally once daily for 28 days. |
| Geriatric use | Not indicated for use after menopause. In perimenopausal women, same adult dosing applies; monitor for increased risk of thromboembolism, hypertension, and carbohydrate intolerance. |
| 1st trimester | Contraindicated due to risk of teratogenicity; however, inadvertent use is not associated with major malformations. |
| 2nd trimester | Contraindicated due to potential adverse effects on fetal development and risk of fetal genital abnormalities from androgenic progestins. |
| 3rd trimester | Contraindicated due to risk of feminization of male fetus and potential metabolic disturbances in the newborn. |
Clinical note
Comprehensive clinical and safety monograph for NORINYL 1+35 28-DAY (NORINYL 1+35 28-DAY).
| Placental transfer | Readily crosses the placenta; fetal plasma levels are approximately 40-80% of maternal levels for norethindrone; ethinyl estradiol crosses with lower efficiency. |
| Breastfeeding | Excreted in breast milk in small amounts; may reduce milk production and quality. Use alternative contraception if possible, especially in early postpartum period. |
| Lactation Rating | L3 (Moderately Safe) or 'Avoid' if alternatives exist, particularly in lactating women with low milk supply. |
| Teratogenic Risk | First trimester: No increased risk of major birth defects from inadvertent exposure. Second and third trimesters: Avoid use due to risk of fetal harm from estrogen/progestin exposure; association with placental abruption, fetal growth restriction, and preterm delivery. |
| Fetal Monitoring | Monitor blood pressure, liver function, and signs of thromboembolism. Perform fetal growth ultrasound if used inadvertently in later pregnancy. |
| Fertility Effects | Normal ovulation and fertility return promptly after discontinuation. No evidence of permanent impairment. |
■ FDA Black Box Warning
Cigarette smoking increases the risk of serious cardiovascular adverse events from combined hormonal contraceptive use. This risk increases with age, especially in women over 35, and with the number of cigarettes smoked. Women who use combined hormonal contraceptives should be strongly advised not to smoke.
| Serious Effects |
PregnancyBreast cancer (current or history)Undiagnosed abnormal uterine bleedingLiver tumors (benign or malignant) or active liver diseaseKnown or suspected estrogen-dependent neoplasiaThrombophlebitis or thromboembolic disorders (current or history)Cerebrovascular or coronary artery diseaseHeavy smoking (≥15 cigarettes/day) and age ≥35Hypertension (uncontrolled or severe)
| Precautions | Increased risk of thromboembolic disorders; liver disease; hypertension; gallbladder disease; carbohydrate and lipid effects; headache; irregular bleeding; ectopic pregnancy; depression; cervical cancer; hereditary angioedema; chloasma; retinal thrombosis; monitoring of blood pressure, glucose, lipids, liver function. |
| Food/Dietary | No significant food interactions. Grapefruit juice may increase estrogen levels; advise limited consumption. Take with food to reduce gastrointestinal upset. Avoid St. John's Wort as it may reduce contraceptive efficacy. |
| Clinical Pearls | Norinyl 1+35 (norethindrone 1 mg/ethinyl estradiol 35 mcg) is a monophasic combined oral contraceptive. Missed pill management: if one active pill missed, take as soon as remembered; if two missed in week 1 or 2, take two pills on day remembered and two on next day; if two missed in week 3 or three missed at any time, discard remainder of pack and start new pack next day. Use backup contraception for 7 days after any miss. Advise to take at same time daily to maintain consistent hormone levels. Monitor for thromboembolic events; absolute contraindication if history of DVT/PE or migraine with aura. Prescribe with caution in smokers over 35 years old. |
| Patient Advice | Take one tablet daily at the same time, preferably after the evening meal to reduce nausea. · Start the first pill on the first day of menstrual period for immediate contraceptive protection. · If you miss a pill, refer to the package insert or call your healthcare provider. · Use a back-up contraceptive method (e.g., condoms) for the first 7 days if starting after day 5 of your cycle. · Common side effects include nausea, breast tenderness, and breakthrough bleeding, which often improve after 3 months. · Seek medical attention for severe abdominal pain, chest pain, leg swelling, or severe headache. · Do not smoke while taking this medication, especially if over 35 years old, due to increased risk of blood clots. · This medication does not protect against HIV or other sexually transmitted infections. |
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