Comparative Pharmacology
Head-to-head clinical analysis: LEVONEST versus NORINYL 1 80 28 DAY.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LEVONEST versus NORINYL 1 80 28 DAY.
LEVONEST vs NORINYL 1+80 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.
Combination oral contraceptive containing a progestin (norethindrone) and an estrogen (mestranol). Suppresses gonadotropin (FSH and LH) release via negative feedback, inhibiting ovulation. Also induces changes in cervical mucus and endometrium to impede sperm penetration and implantation.
One tablet (levonorgestrel 1.5 mg) orally as a single dose within 72 hours of unprotected intercourse.
One tablet (1 mg norethindrone / 80 mcg ethinyl estradiol) orally once daily for 28-day cycle without placebo.
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: terminal elimination half-life of 5.3-10.5 hours; Mestranol (as ethinyl estradiol): terminal half-life of 7-20 hours. Clinically, steady state is achieved after 5-7 days of daily dosing; the half-life supports once-daily dosing for consistent hormonal levels.
Renal excretion of conjugated metabolites accounts for approximately 60-80% of an administered dose; fecal elimination via bile accounts for 20-40%.
Norethindrone is primarily excreted in urine (approximately 60%) and feces (approximately 40%) as glucuronide and sulfate conjugates. Mestranol is metabolized to ethinyl estradiol; ethinyl estradiol and its metabolites are excreted in urine (40%) and feces (60%).
Category C
Category C
Oral Contraceptive
Oral Contraceptive