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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TRI-NORINYL 21-DAY (TRI-NORINYL 21-DAY).
| Breastfeeding | Norethindrone and ethinyl estradiol are excreted in human milk in small amounts (<1% of maternal dose). The estimated M/P ratio for norethindrone is 0.5–1.0; for ethinyl estradiol, <0.1. May reduce milk quantity and quality due to estrogenic suppression of prolactin. Use is not recommended during breastfeeding; advise alternative contraception. |
| 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. |
■ 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 |
Thrombophlebitis or thromboembolic disorders; cerebrovascular or coronary artery disease; known/suspected breast carcinoma; endometrial carcinoma or other estrogen-dependent neoplasia; undiagnosed abnormal genital bleeding; cholestatic jaundice of pregnancy/jaundice with prior pill use; hepatic adenoma/carcinoma; known/suspected pregnancy; hypersensitivity to any component; use with Hepatitis C drug combinations containing ombitasvir/paritaprevir/ritonavir with or without dasabuvir.
| 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. |
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| 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. |