TRI-NORINYL 21-DAY
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TRI-NORINYL 21-DAY (TRI-NORINYL 21-DAY).
Combination oral contraceptive containing ethinyl estradiol and norethindrone. Ethinyl estradiol suppresses gonadotropin release via negative feedback on hypothalamic-pituitary axis; norethindrone induces progestational effects, increases viscosity of cervical mucus, alters endometrial morphology, and inhibits ovulation.
| Metabolism | Metabolized primarily via CYP3A4; ethinyl estradiol undergoes hydroxylation and conjugation; norethindrone undergoes reduction and conjugation. |
| Excretion | Renal: ~50-60% (as metabolites); Fecal: ~30-40% (via bile); unchanged drug <1%. |
| Half-life | Norethindrone: 5-14 hours; Ethinyl estradiol: 17-23 hours. Steady-state reached within 5-7 days; clinical relevance for missed dose timing and resumption of ovulation. |
| Protein binding | Norethindrone: ~61% bound to albumin and SHBG; Ethinyl estradiol: ~98% bound to albumin (inducible SHBG binding). |
| Volume of Distribution | Norethindrone: ~3.6 L/kg; Ethinyl estradiol: ~2.9 L/kg. Indicates extensive tissue distribution. |
| Bioavailability | Oral: Norethindrone ~64% (first-pass metabolism); Ethinyl estradiol ~45% (interindividual variability due to gut and liver metabolism). |
| Onset of Action | Oral: Contraceptive effect begins after 7 consecutive days of active pills (if started on Day 1 of menses); 2-3 days for full hypothalamic-pituitary-ovarian suppression. |
| Duration of Action | 24 hours per active pill; withdrawal bleed occurs during 7-day placebo interval; ovulation suppression maintained with continuous adherence. |
| Molecular Weight | 340.46 |
One tablet (35 mcg ethinyl estradiol, 0.5 mg norethindrone for 7 days, 1 mg norethindrone for 9 days, 0.5 mg norethindrone for 5 days) orally once daily for 21 days, then 7 days off. Start on first day of menstrual period or first Sunday after onset.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. Not studied in severe renal impairment (GFR <30 mL/min); use contraindicated or only if benefit outweighs risk due to potential fluid retention. |
| Liver impairment | Contraindicated in acute hepatic disease, active hepatitis, or Child-Pugh class B or C cirrhosis. Use with caution in mild hepatic impairment (Child-Pugh A) with monitoring of liver function; dose adjustment not defined. |
| Pediatric use | Post-menarche adolescents: Same as adult dosing. Not indicated for pre-menarche use. Safety and efficacy established for contraception in adolescents. |
| Geriatric use | Not indicated for postmenopausal women. No specific geriatric dosing; use not recommended due to increased thromboembolic risk and lack of need for contraception. |
| 1st trimester | Contraindicated due to risk of congenital anomalies including cardiovascular defects and limb reduction. Estrogen/progestin combinations are not recommended during pregnancy. |
| 2nd trimester | Contraindicated; can cause fetal harm. Use of oral contraceptives during pregnancy is associated with increased risk of fetal abnormalities. |
| 3rd trimester | Contraindicated; may cause adverse effects on fetal development and neonatal complications. |
Clinical note
Comprehensive clinical and safety monograph for TRI-NORINYL 21-DAY (TRI-NORINYL 21-DAY).
| Placental transfer | Both ethinyl estradiol and norethindrone cross the placenta. Norethindrone achieves fetal serum levels approximately 10-20% of maternal levels; ethinyl estradiol transfer is limited but detectable. |
| Breastfeeding | Small amounts of ethinyl estradiol and norethindrone are excreted in breast milk. May reduce milk production and affect infant growth. Use is generally not recommended during breastfeeding. Alternative contraception should be considered. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular side effects from oral contraceptive use. Risk increases with age and heavy smoking (≥15 cigarettes/day) and is significant in women >35 years old. Women >35 who smoke should not use combination oral contraceptives.
| Serious Effects |
Pregnancy or suspected pregnancyThromboembolic disordersHistory of deep vein thrombosis or pulmonary embolismCerebrovascular diseaseCoronary artery diseaseLiver disease or tumorBreast cancer or other estrogen-dependent neoplasiaUndiagnosed abnormal genital bleedingKnown or suspected carcinoma of endometriumCholestatic jaundice of pregnancy or jaundice with prior oral contraceptive use
| Precautions | Increased risk of thromboembolic disorders (myocardial infarction, stroke, deep vein thrombosis, pulmonary embolism); hepatic neoplasia; increased blood pressure; gallbladder disease; carbohydrate/lipid effects; headache; irregular bleeding; use in pregnancy must be excluded. |
| Food/Dietary | No specific food restrictions. Grapefruit juice may increase ethinyl estradiol levels but clinically insignificant in standard use. Consistent intake with food may reduce nausea. Avoid excessive alcohol as it may increase liver burden and affect hormone levels. |
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| Lactation Rating | L4 - Possibly Hazardous |
| Teratogenic Risk | Pregnancy category X. Use is contraindicated throughout pregnancy. First trimester: Increased risk of neural tube defects, congenital heart defects, and limb reduction defects due to estrogen and progestin exposure. Second and third trimesters: Associated with masculinization of female fetuses from the progestin component (norethindrone), and potential for adrenal suppression in neonates. Postnatal follow-up for endocrine effects is recommended if inadvertent exposure occurs. |
| Fetal Monitoring | No monitoring required as use is contraindicated in pregnancy. For inadvertent exposure: confirm pregnancy status via quantitative hCG, perform ultrasound for fetal anatomy assessment if exposure occurred in first trimester, monitor neonatal adrenal function at birth if exposure in late pregnancy. |
| Fertility Effects | TRI-NORINYL is an oral contraceptive; intended to suppress ovulation and prevent pregnancy. Fertility typically returns to baseline within 1–3 months after discontinuation. No long-term impairment of female fertility observed. No effect on spermatogenesis or male fertility. |
| Clinical Pearls | Tri-Norinyl (norethindrone/ethinyl estradiol) is a monophasic combined oral contraceptive. Counsel patients on strict adherence to a 21-day regimen with 7-day hormone-free interval. Bleeding irregularities are common in first 3 cycles; if persistent, consider non-adherence or alternative formulation. Estrogen-containing contraceptives increase thrombotic risk; contraindicated in smokers over 35, hypertension (systolic ≥160 or diastolic ≥100), migraine with aura, or history of VTE. Drug interactions with rifampin, certain anticonvulsants (e.g., carbamazepine, phenytoin), and St. John's wort may reduce efficacy; consider backup contraception. |
| Patient Advice | Take one tablet daily at the same time each day for 21 days, then none for 7 days; start next pack on the same day of the week you started the first. · If you miss a pill, follow the package instructions; use backup contraception if needed. · Do not smoke while taking this medication, especially if over 35, due to increased risk of blood clots. · Contact your doctor immediately if you experience severe leg pain, chest pain, shortness of breath, severe headache, or vision changes. · This medication does not protect against sexually transmitted infections; use condoms for STI prevention. |