LARIN FE 1/20
Clinical safety rating
cautionComprehensive clinical and safety monograph for LARIN FE 1/20 (LARIN FE 1/20).
LARIN FE 1/20 is a combination oral contraceptive containing ethinyl estradiol and norethindrone. It inhibits ovulation by suppressing gonadotropin release (FSH and LH) from the pituitary, increases viscosity of cervical mucus, and alters endometrial receptivity.
| Metabolism | Ethinyl estradiol is metabolized primarily via CYP3A4, with sulfation and glucuronidation. Norethindrone is reduced and conjugated, primarily via CYP3A4 and other CYP450 enzymes. |
| Excretion | Renal (60% as metabolites, <10% unchanged); biliary/fecal (40%) |
| Half-life | Ethinyl estradiol: ~13 hours (range 7-20); norethindrone: ~8-11 hours. Steady-state reached in 5-7 days. |
| Protein binding | Ethinyl estradiol: 97-98% (albumin, SHBG); norethindrone: 80-85% (albumin, SHBG) |
| Volume of Distribution | Ethinyl estradiol: 2.5-5 L/kg; norethindrone: 2-4 L/kg. Indicates extensive tissue distribution. |
| Bioavailability | Oral: ~40% for ethinyl estradiol (first-pass metabolism); ~64% for norethindrone (range 50-75%) |
| Onset of Action | Oral: Ovulation suppression begins within 1-2 days of starting regimen; full contraceptive effect after 7 days of continuous use. |
| Duration of Action | Oral: Duration of contraceptive effect is 24 hours; requires daily dosing. After discontinuation, ovulation may resume in 1-3 months. |
| Molecular Weight | Ethinyl estradiol: 296.4 Da; Norethindrone acetate: 340.5 Da (combination product average ~318 Da) |
| Action Class | Combination Oral Contraceptive (Estrogen-Progestin) |
One tablet orally once daily for 21 consecutive days, followed by 7 days of placebo (ferrous fumarate) tablets per cycle.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. Severe renal impairment (GFR <30 mL/min) may require monitoring due to potential fluid retention; use lowest effective dose. |
| Liver impairment | Contraindicated in Child-Pugh class C cirrhosis. For Child-Pugh class B, use with caution and only if benefits outweigh risks; consider alternative methods of contraception. Child-Pugh class A: no adjustment necessary. |
| Pediatric use | Approved for post-menarcheal adolescents. Same dosing as adults: one active tablet daily for 21 days, then placebo for 7 days. Weight-based adjustments not required. |
| Geriatric use | Not indicated for postmenopausal women. No specific geriatric dose adjustments, but consider increased risk of thrombotic events and manage cardiovascular risk factors. |
| 1st trimester | Contraindicated due to risk of birth defects and pregnancy loss; use only if benefit outweighs risk. |
| 2nd trimester | Contraindicated due to potential adverse effects on fetal development; not recommended. |
| 3rd trimester | Contraindicated due to potential adverse effects on fetal development; not recommended. |
Clinical note
Comprehensive clinical and safety monograph for LARIN FE 1/20 (LARIN FE 1/20).
| Placental transfer | Both components cross the placenta; ethinyl estradiol is highly protein-bound, reducing transfer, but norethindrone acetate and its metabolites cross readily. |
| Breastfeeding | Small amounts of ethinyl estradiol and norethindrone acetate pass into breast milk; may affect milk production and composition. Use only when necessary, with caution. |
| Lactation Rating | L4 - Possibly hazardous |
| Teratogenic Risk | Pregnancy category X. Use contraindicated in pregnancy due to known teratogenicity. First-trimester exposure associated with cardiovascular defects and limb reduction defects. Second and third trimesters: no increased risk of malformations but potential for adverse effects from progestational agents and estrogen. Risk of fetal genital abnormalities with prolonged exposure. |
| Fetal Monitoring | Monitor pregnancy test before initiation and at each visit. If pregnancy occurs, discontinue immediately. For inadvertent use, perform detailed fetal ultrasound for structural anomalies. Monitor for signs of thromboembolism in mother. |
| Fertility Effects | No known permanent adverse effects on fertility. Oral contraceptives may delay return to fertility after discontinuation, but fertility typically returns within 1-2 cycles. No evidence of impaired long-term fertility. |
■ FDA Black Box Warning
Cigarette smoking increases the risk of serious cardiovascular side effects from oral contraceptive use. The risk increases with age and with heavy smoking (≥15 cigarettes per day) and is quite marked in women >35 years of age. Women who use oral contraceptives should be strongly advised not to smoke.
| Common Effects | Nausea, Headache, Breast tenderness, Weight changes, Irregular uterine bleeding, Mood changes |
| Serious Effects | Venous thromboembolism, Arterial thromboembolism (e.g., stroke, myocardial infarction), Hepatic adenoma or hepatocellular carcinoma, Hypertension, Gallbladder disease, Cholestatic jaundice |
Thrombophlebitis or thromboembolic disordersCerebrovascular or coronary artery diseaseKnown or suspected pregnancyUndiagnosed abnormal genital bleedingKnown or suspected breast cancerBenign or malignant liver tumorActive liver disease or impaired liver functionHypersensitivity to any component
| Precautions | Thrombotic disorders: Risk of venous thromboembolism, arterial thrombosis, stroke, myocardial infarction., Hepatic disease: Discontinue if jaundice or cholestasis develops., Hypertension: Monitor blood pressure; may cause new-onset or worsening hypertension., Gallbladder disease: Increased risk of gallstones., Carbohydrate metabolism: May impair glucose tolerance., Hypertriglyceridemia: May cause pancreatitis if elevated., Uterine bleeding: Discontinue if unexplained amenorrhea or irregular bleeding persists., Ocular disorders: Retinal thrombosis; discontinue if sudden partial or complete vision loss., Depression: May recur or worsen., Toxic shock syndrome: Associated with use of vaginal rings, but not specifically with this pill. |
| Food/Dietary | No significant food interactions. However, grapefruit juice may slightly increase ethinyl estradiol levels; avoid large amounts. The ferrous fumarate in placebo pills may cause gastrointestinal upset; take with food if needed. |
| Clinical Pearls | LARIN FE 1/20 is a combination oral contraceptive containing norethindrone acetate (1 mg) and ethinyl estradiol (20 mcg). It uses a 24/4 regimen with 24 active pills and 4 ferrous fumarate placebo pills. The iron supplements in the placebo pills help reduce the risk of iron deficiency anemia. Advise patients that spotting or breakthrough bleeding is common in the first few cycles. Monitor for hypertension, migraines, and thrombotic events. Smoking increases cardiovascular risk, especially in women over 35. LARIN FE 1/20 may decrease milk production in breastfeeding women. |
| Patient Advice | Take one pill daily at the same time each day. Swallow the pill whole; do not crush or chew. · Start the pack on the first Sunday after your period starts (unless instructed otherwise). · Use backup contraception (like condoms) for the first 7 days if you start taking the pill for the first time. · If you miss a pill, refer to the package insert for instructions. Missing pills increases pregnancy risk. · Common side effects include nausea, breast tenderness, and breakthrough bleeding. These often improve after a few months. · Contact your healthcare provider if you experience severe abdominal pain, chest pain, sudden shortness of breath, severe headaches, vision changes, or leg pain/swelling (possible blood clots). · Talk to your doctor before starting if you smoke, are over 35, have high blood pressure, migraines with aura, or a history of blood clots. · The iron pills (brown tablets) are not active birth control; they are taken during the fourth week to help prevent anemia. · Do not stop taking the pill without consulting your doctor. |
Loading safety data…