LO LARIN FE
Clinical safety rating
cautionComprehensive clinical and safety monograph for LO LARIN FE (LO LARIN FE).
Combination of ethinyl estradiol (estrogen) and norethindrone (progestin) inhibits gonadotropin release, preventing ovulation; increases cervical mucus viscosity, impeding sperm penetration; alters endometrial lining, reducing implantation likelihood.
| Metabolism | Ethinyl estradiol: primarily metabolized via CYP3A4; norethindrone: reduced to active metabolite (ethynylestradiol) and also metabolized via CYP3A4. Both undergo conjugation (glucuronidation and sulfation). |
| Excretion | Renal: 30-50% as ethinyl estradiol metabolites and norethindrone metabolites; fecal: 30-50% primarily as norethindrone metabolites; biliary excretion contributes to enterohepatic circulation. |
| Half-life | Ethinyl estradiol: ~13-17 hours; norethindrone: ~8-12 hours; steady-state achieved within 5-7 days; clinical significance: missed doses may require backup contraception. |
| Protein binding | Ethinyl estradiol: ~97-98% bound to albumin and sex hormone-binding globulin (SHBG); norethindrone: ~90-95% bound to albumin and SHBG. |
| Volume of Distribution | Ethinyl estradiol: ~3-4 L/kg; norethindrone: ~4-5 L/kg; indicates extensive tissue distribution beyond plasma volume. |
| Bioavailability | Oral: ethinyl estradiol ~40-50% (first-pass metabolism); norethindrone ~60-70% (low first-pass effect). |
| Onset of Action | Oral: maximum contraceptive effect after 7 days of continuous dosing; immediate effect if started on day 1 of menstrual cycle. |
| Duration of Action | 24 hours per dose; contraceptive protection maintained with daily adherence; missed dose >24 hours increases pregnancy risk. |
| Molecular Weight | Ethinyl estradiol: 296.4 Da; Norethindrone acetate: 340.5 Da (component weights; combination product not a single molecule) |
| Action Class | Oral Contraceptive; Estrogen-Progestin Combination |
One tablet orally once daily for 28 consecutive days. Each tablet contains norethindrone acetate 1 mg and ethinyl estradiol 20 mcg. Active tablets (21 days) followed by ferrous fumarate 75 mg inert tablets (7 days).
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. Contraindicated in acute renal disease or renal impairment with decreased renal function due to potential fluid retention and hyperkalemia. |
| Liver impairment | Contraindicated in acute hepatic disease, hepatic adenoma, or history of cholestatic jaundice. For mild Child-Pugh A: no data; use with caution. Moderate to severe (Child-Pugh B or C): contraindicated. |
| Pediatric use | Not indicated for use before menarche. Post-menarche adolescents: same dosing as adults (one tablet daily) with monitoring for thromboembolic risk. |
| Geriatric use | Not indicated for use in postmenopausal women. No specific geriatric dosing; avoid in women over 50 due to increased cardiovascular and thromboembolic risks. |
| 1st trimester | Contraindicated; may cause fetal harm if pregnancy occurs. Combination oral contraceptives present risk of fetal androgen exposure and potential teratogenicity (e.g., cardiovascular defects, limb reductions) based on animal studies and human case reports. Use during first trimester should be avoided unless necessary for treatment of heavy menstrual bleeding or dysmenorrhea, though alternatives preferred. |
| 2nd trimester | Contraindicated; fetal risk remains during second trimester due to ongoing organogenesis and potential for sex hormone disruption. Use only if no other option and patient is adequately informed. |
| 3rd trimester | Contraindicated; risk of fetal harm persists. Estrogen-progestin combinations may cause urogenital sinus abnormalities and other effects. Use not recommended. |
Clinical note
Comprehensive clinical and safety monograph for LO LARIN FE (LO LARIN FE).
| Placental transfer | Both ethinyl estradiol and norethindrone acetate cross the placenta. Ethinyl estradiol has a placental transfer ratio of approximately 0.5-0.7 (maternal:fetal cord blood levels). Norethindrone acetate is extensively transferred, with fetal serum levels reaching 10-30% of maternal levels. These steroids may cause adverse effects on fetal genital development and other tissues. |
| Breastfeeding | Combination oral contraceptives (COCs) containing estrogen and progestin may reduce milk production and alter milk composition, especially during the first weeks postpartum. Small amounts of contraceptive steroids and/or metabolites are excreted in breast milk, but no adverse effects on infant development have been reported with progestin-only methods. Use of COCs during breastfeeding is associated with decreased milk volume and earlier weaning. If contraception is needed, progestin-only pills or non-hormonal methods are preferred for lactating women. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Pregnancy category X. Contraindicated in pregnancy. First trimester: Risk of cardiovascular defects, oral clefts, neural tube defects. Second and third trimesters: Risk of feminization of male fetus, hepatic adenoma, and possible reduced birth weight. |
| Fetal Monitoring | Monitor blood pressure, liver function, glucose tolerance, and signs of thromboembolism. Ultrasound for fetal anomalies if inadvertent exposure. |
| Fertility Effects | May delay return to fertility after discontinuation due to ovulation suppression, but no permanent negative effects on fertility. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular events from combination oral contraceptives. Risk increases with age and heavy smoking (≥15 cigarettes/day). Women over 35 who smoke should not use this product.
| Common Effects | Nausea, Vomiting, Headache, Breast tenderness, Breakthrough bleeding or spotting, Weight changes, Mood changes, Acne, Fluid retention, Melasma (chloasma) |
| Serious Effects | Venous thromboembolism (VTE) including deep vein thrombosis and pulmonary embolism, Arterial thromboembolism (e.g., stroke, myocardial infarction), Hepatic adenoma or hepatocellular carcinoma, Hypertension, Gallbladder disease, Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) (rare), Retinal thrombosis |
Known or suspected pregnancyCurrent or history of venous thromboembolism (e.g., deep vein thrombosis, pulmonary embolism)Active or history of arterial thromboembolism (e.g., stroke, myocardial infarction) or prodromal conditions (e.g., angina, transient ischemic attack)Breast cancer or other estrogen-sensitive neoplasia, known or suspectedLiver tumors (benign or malignant) or active liver disease (e.g., hepatitis, cirrhosis)Undiagnosed abnormal genital bleedingMigraine with aura (especially if over age 35 or with focal neurological symptoms)Major surgery with prolonged immobilizationDiabetes with vascular involvementUncontrolled hypertension (sustained BP ≥140/90 mmHg)Cigarette smoking in women over 35 years of ageSevere hypertriglyceridemia (≥500 mg/dL)Known thrombophilia (e.g., factor V Leiden, prothrombin mutation, protein S/C deficiency)Systemic lupus erythematosus with positive antiphospholipid antibodiesPulmonary hypertensionAcute viral hepatitis or decompensated cirrhosis
| Precautions | Thromboembolic disorders (VTE, stroke, MI) - increased risk especially in smokers >35, Carcinogenesis: possible increased risk of breast and cervical cancer, Hepatic effects: cholestatic jaundice, liver tumors, Gallbladder disease, Elevated blood pressure, COC use does not protect against HIV or other STDs, Ocular changes: retinal thrombosis, contact lens intolerance, Depression, Reduced efficacy with enzyme-inducing drugs |
| Food/Dietary | No significant food interactions. Grapefruit juice may slightly increase estrogen levels but is generally not a concern. Iron absorption from the placebo pills is enhanced by taking with vitamin C (e.g., citrus fruits). |
| Clinical Pearls | LO LARIN FE is a combination oral contraceptive containing norethindrone acetate and ethinyl estradiol with ferrous fumarate as a dietary supplement. Advise patients to take the active pills at the same time daily to maintain consistent hormone levels. The iron in the placebo pills is not sufficient for treating anemia but helps maintain iron stores. Instruct patients to start the first pack on the first day of menstrual bleeding. Missed doses increase the risk of breakthrough bleeding and contraceptive failure. Counsel that use of certain anticonvulsants, antibiotics, or St. John's wort can reduce efficacy. |
| Patient Advice | Take one tablet daily at the same time each day. Do not skip doses. · The 24th to 28th pills are placebo and contain iron; they are not for contraception. · If you miss a dose, refer to the package insert instructions. Two missed pills may require backup contraception. · Smoking increases the risk of serious cardiovascular side effects, especially if you are over 35. · Report symptoms of blood clots, such as leg pain, chest pain, or sudden shortness of breath immediately. · This medication does not protect against sexually transmitted infections. |
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