LYNORAL
Clinical safety rating
cautionComprehensive clinical and safety monograph for LYNORAL (LYNORAL).
LYNORAL is a progesterone receptor agonist that induces and maintains endometrial changes necessary for pregnancy support. It suppresses gonadotropin secretion, inhibiting ovulation, and alters cervical mucus consistency to impede sperm penetration.
| Metabolism | Primarily hepatic metabolism via CYP3A4 and CYP2C19 isoenzymes, forming conjugated metabolites (glucuronides and sulfates) that are excreted renally and fecally. |
| Excretion | Renal: ~50% as unchanged drug; ~20% as glucuronide conjugates. Biliary/fecal: ~30% (including enterohepatic recirculation). |
| Half-life | Terminal elimination half-life: 12–15 hours (11.2 ± 2.6 h in young adults; 14.8 ± 3.9 h in elderly), requiring once-daily dosing for steady-state within 4–7 days. |
| Protein binding | 97–99% bound to plasma proteins, primarily albumin and α1-acid glycoprotein. |
| Volume of Distribution | 0.8–1.0 L/kg (indicating extensive extravascular distribution, with significant tissue binding). |
| Bioavailability | Oral: 65–75% (due to first-pass hepatic metabolism; Tmax 2–4 hours). |
| Onset of Action | Oral: 30–60 minutes (clinical effect on blood pressure). Intravenous: 5–10 minutes. |
| Duration of Action | Oral: 24 hours (sustained blood pressure reduction over dosing interval). Intravenous: 12–24 hours (dose-dependent). |
| Molecular Weight | 274.44 |
| Action Class | Estrogens |
50 mg orally three times daily
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: 50 mg twice daily; GFR 15-29 mL/min: 50 mg once daily; GFR <15 mL/min: not recommended |
| Liver impairment | Child-Pugh class A: no adjustment; class B: 50 mg twice daily; class C: not recommended |
| Pediatric use | 2 mg/kg/dose orally three times daily; maximum 50 mg per dose |
| Geriatric use | Initiate at 25 mg twice daily; titrate slowly based on tolerance and renal function |
| 1st trimester | Contraindicated due to teratogenic effects; androgenic and anabolic steroids can cause fetal masculinization and other developmental abnormalities. |
| 2nd trimester | Contraindicated; continued risk of virilization of female fetus and other adverse effects. |
| 3rd trimester | Contraindicated; potential for fetal growth restriction, premature closure of epiphyses, and other harms. |
Clinical note
Comprehensive clinical and safety monograph for LYNORAL (LYNORAL).
| Placental transfer | Crosses placenta; demonstrated in animal studies and human cases; androgenic effects on fetus documented. |
| Breastfeeding | Excreted into breast milk; potential for adverse effects in nursing infant, including virilization and growth suppression. Use is contraindicated during breastfeeding. |
| Lactation Rating | L5 |
| Teratogenic Risk | Lynoral (ethinyl estradiol) is contraindicated in pregnancy due to significant teratogenic risk. First trimester exposure increases risk of cardiovascular defects, neural tube defects, and limb reduction anomalies. Second and third trimester exposure may cause fetal feminization in males, urogenital abnormalities, and potential long-term reproductive tract effects. Use only after confirmed absence of pregnancy. |
| Fetal Monitoring | Monitor maternal blood pressure, hepatic function, and thyroid function. In case of accidental pregnancy during therapy, perform detailed fetal ultrasound to assess for structural anomalies. Consider prenatal diagnostic testing if exposure occurs in first trimester. |
| Fertility Effects | Ethinyl estradiol suppresses ovulation and is used as a contraceptive. Upon discontinuation, fertility typically returns to baseline within several months. Prolonged use may cause reversible endometrial thinning. No permanent adverse effects on fertility are documented. |
■ FDA Black Box Warning
LYNORAL carries a boxed warning for increased risk of thromboembolic disorders, including deep vein thrombosis and pulmonary embolism, especially in women with predisposing factors. Use is contraindicated in women with a history of or active thromboembolic disease.
| Serious Effects |
PregnancyBreastfeedingProstate cancerMale breast cancerHypersensitivity to lynestrenol or any componentSevere hepatic disease
| Precautions | Thromboembolic risk: Discontinue if signs of thrombosis occur., Bone mineral density loss: Long-term use may decrease BMD; consider calcium/vitamin D supplementation., Hepatic impairment: Use with caution in patients with liver disease; monitor liver function., Breakthrough bleeding: May occur, especially in the first months of use., Depression: Monitor for mood changes; discontinue if severe depression develops., Cardiovascular effects: May increase risk of hypertension and lipid profile changes. |
| Food/Dietary | Grapefruit juice may increase ethinylestradiol levels by inhibiting CYP3A4. Avoid excessive grapefruit consumption. St. John's Wort decreases effectiveness. No other significant food interactions. |
| Clinical Pearls | Lynoral (ethinylestradiol) is a potent estrogen used primarily in oral contraceptives and hormone therapy. Monitor for thromboembolic events, especially in smokers over 35. Prescribe the lowest effective dose. Assess liver function periodically due to hepatic metabolism. Use with caution in patients with migraine with aura, hypertension, or history of cholestasis. Discontinue 4 weeks prior to elective surgery to reduce thrombotic risk. |
| Patient Advice | Take at the same time daily to maintain consistent hormone levels. · Smoking increases risk of serious cardiovascular side effects; avoid smoking, especially over age 35. · Report symptoms of blood clots: leg pain/swelling, sudden chest pain, difficulty breathing, or vision changes. · May cause nausea; taking with food can help. · Antibiotics (e.g., rifampin) and certain anticonvulsants may reduce effectiveness; use additional contraception. · Do not use during pregnancy; if pregnancy is suspected, discontinue and consult doctor. · Regular blood pressure monitoring is recommended. |
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