TRI-NORINYL 28-DAY
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TRI-NORINYL 28-DAY (TRI-NORINYL 28-DAY).
Combination oral contraceptive containing ethinyl estradiol and norethindrone. Suppresses gonadotropin (FSH and LH) release via negative feedback, inhibiting ovulation. Also increases viscosity of cervical mucus and alters endometrial lining to reduce implantation likelihood.
| Metabolism | Ethinyl estradiol primarily metabolized by CYP3A4 via hydroxylation. Norethindrone metabolized by CYP3A4 and CYP2C9. Both undergo conjugation (glucuronidation and sulfation). |
| Excretion | Renal: 40% as metabolites; Fecal: 50% as metabolites; Biliary: minor; unchanged ethinyl estradiol excreted in urine <5%, norethindrone <1%. |
| Half-life | Ethinyl estradiol: 17 ± 6 hours (terminal); Norethindrone: 10 ± 3 hours (terminal). Steady-state achieved after 7-14 days. |
| Protein binding | Ethinyl estradiol: 97-98% (albumin 70%, SHBG 30%); Norethindrone: 95-99% (albumin 61%, SHBG 38%). |
| Volume of Distribution | Ethinyl estradiol: 2.7-3.1 L/kg; Norethindrone: 4.8-5.3 L/kg. Indicates extensive tissue distribution. |
| Bioavailability | Oral: Ethinyl estradiol 38-48% (first-pass metabolism); Norethindrone 64-65% (first-pass metabolism). |
| Onset of Action | Oral: Contraceptive effect requires 7 days of continuous dosing (if starting not on day 1 of menses). No immediate effect. |
| Duration of Action | Oral: Contraceptive coverage persists for 24 hours per active pill; after last active pill, protection continues for 7 days (placebo period). |
| Molecular Weight | 368.47 |
One tablet orally once daily for 21 days, followed by one placebo tablet orally once daily for 7 days. Each active tablet contains 0.035 mg ethinyl estradiol and 0.5 mg norethindrone (7 days), 0.035 mg ethinyl estradiol and 1.0 mg norethindrone (9 days), and 0.035 mg ethinyl estradiol and 0.5 mg norethindrone (5 days).
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment required based on GFR. Contraindicated in patients with acute or chronic hepatic dysfunction with impaired renal function. |
| Liver impairment | Contraindicated in patients with acute or chronic hepatic disease (Child-Pugh class B or C). For Child-Pugh class A, use with caution and monitor liver function; no specific dose adjustment available. |
| Pediatric use | Not indicated for use before menarche. After menarche, standard adult dosing applies. |
| Geriatric use | Not indicated for use after menopause. No specific geriatric dose adjustment required if used off-label in perimenopausal women, but consider increased risk of cardiovascular events and venous thromboembolism. |
| 1st trimester | Contraindicated in first trimester due to risk of congenital defects (e.g., cardiovascular, limb defects). Use only if no alternative and benefits outweigh risks. |
| 2nd trimester | Contraindicated due to potential for fetal harm, including masculinization of female fetus if androgenically active. |
| 3rd trimester | Contraindicated; may cause virilization of female fetus, hepatic dysfunction, and adverse pregnancy outcomes. |
Clinical note
Comprehensive clinical and safety monograph for TRI-NORINYL 28-DAY (TRI-NORINYL 28-DAY).
| Placental transfer | Crosses placenta; documented in human and animal studies. Transfers to fetal compartment with potential for teratogenicity. |
| Breastfeeding | Excreted in breast milk; may reduce milk production and quality. Use only if necessary and with caution, monitoring infant for jaundice, hepatotoxicity, and virilization. |
■ FDA Black Box Warning
Cigarette smoking increases the risk of serious cardiovascular adverse events from combination oral contraceptive use. 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 |
Pregnancy or suspected pregnancyHypersensitivity to norethindrone or ethinyl estradiolCholestatic jaundice of pregnancy or history of jaundice with prior OCsHepatic adenoma or carcinomaUndiagnosed abnormal genital bleeding
| Precautions | Thrombotic disorders (thrombophlebitis, pulmonary embolism, stroke, myocardial infarction), especially in smokers and women over 35, Hepatic neoplasia (benign and malignant liver tumors), Gallbladder disease (increased risk of gallstones), Hypertension (may develop or worsen), Carbohydrate metabolism effects (reduced glucose tolerance, insulin resistance), Ocular lesions (retinal thrombosis, optic neuritis) |
| Food/Dietary | Grapefruit juice may increase ethinyl estradiol levels by inhibiting CYP3A4, potentially increasing side effects. Avoid large quantities of grapefruit juice. No specific food restrictions. St. John's Wort, an herbal supplement, can reduce contraceptive efficacy. High-fat meals may slightly increase ethinyl estradiol absorption but not clinically significant. |
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| Lactation Rating | L4 (possibly hazardous) |
| Teratogenic Risk | Pregnancy category X. Contraindicated in pregnancy due to risk of fetal harm. First trimester: no increased risk of major malformations from combination oral contraceptives in most studies, but post-marketing reports of fetal abnormalities. Second and third trimesters: associated with increased risk of fetal genital tract abnormalities (e.g., hypospadias, vaginal adenosis) and possible carcinogenic effects. Use during pregnancy is not recommended; discontinue if pregnancy occurs. |
| Fetal Monitoring | Monitor for signs of pregnancy before initiation; perform pregnancy test if pregnancy suspected. During use, monitor for thrombotic events (e.g., DVT, PE), hypertension, liver dysfunction, and gallbladder disease. No specific fetal monitoring required if pregnancy ruled out. In case of accidental use during pregnancy, ultrasonography may be considered to assess fetal anatomy. |
| Fertility Effects | Suppresses ovulation as primary mechanism; fertility is transiently impaired during use. Return to normal fertility typically occurs within 1-3 months after discontinuation. No long-term adverse effects on fertility reported. Does not cause permanent infertility. |
| Clinical Pearls | TRI-NORINYL 28-DAY is a triphasic combined oral contraceptive containing norethindrone and ethinyl estradiol. The varying hormone doses across the 21-day active phase mimic the natural menstrual cycle, potentially reducing breakthrough bleeding. Initiate on the first day of menstrual period for immediate contraceptive effect; if starting on other days, use backup contraception for 7 days. Missed pill management: if one pill is missed, take it as soon as remembered, even if that means taking two pills in one day; if two or more pills are missed, use backup contraception for 7 days and consult package insert. Monitor for thromboembolic risk, especially in smokers over 35, hypertension, or migraine with aura. Counsel about breakthrough bleeding, which is common in the first few cycles. |
| Patient Advice | Take one pill daily at the same time, preferably in the evening to minimize nausea. · The first 21 pills contain hormones; the last 7 are placebo (reminder pills) and a period will occur during that week. · If you miss a pill, refer to the package insert; if you miss two or more, use a backup method like condoms for 7 days. · Do not smoke while taking this medication, especially if over 35, due to increased risk of blood clots. · Common side effects include nausea, breast tenderness, and breakthrough bleeding; these often improve after 2-3 cycles. · Contact your healthcare provider if you experience severe leg pain, chest pain, sudden shortness of breath, or severe headache. · This medication does not protect against sexually transmitted infections (STIs); use condoms for STI prevention. · If you miss a period, consider pregnancy and take a pregnancy test before starting the next pack. |