Comparative Pharmacology
Head-to-head clinical analysis: LEVONEST versus NORINYL 1 50 28 DAY.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LEVONEST versus NORINYL 1 50 28 DAY.
LEVONEST vs NORINYL 1+50 28-DAY
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Levonorgestrel is a synthetic progestin that inhibits ovulation by suppressing luteinizing hormone (LH) surge, alters cervical mucus to impede sperm penetration, and induces endometrial changes that inhibit implantation.
Norethindrone and ethinyl estradiol combination works by suppressing gonadotropin-releasing hormone (GnRH) from the hypothalamus, reducing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion, thereby inhibiting ovulation. Norethindrone also alters cervical mucus viscosity and endometrial lining, impeding sperm penetration and implantation.
One tablet (levonorgestrel 1.5 mg) orally as a single dose within 72 hours of unprotected intercourse.
One tablet orally once daily for 28 days, with 7 inactive tablets during the last 7 days. Each active tablet contains norethindrone 1 mg and ethinyl estradiol 50 mcg.
None Documented
None Documented
The terminal elimination half-life is approximately 24-30 hours. This relatively long half-life supports once-daily dosing and allows for stable plasma concentrations within 5-7 days of continuous use.
Norethindrone: ~8-11 hours; Mestranol: 24 hours (prodrug, ethinyl estradiol half-life ~13-27 hours).
Renal excretion of conjugated metabolites accounts for approximately 60-80% of an administered dose; fecal elimination via bile accounts for 20-40%.
Renal: ~40% as metabolites; Biliary/Fecal: ~60% as metabolites.
Category C
Category C
Oral Contraceptive
Oral Contraceptive