Comparative Pharmacology
Head-to-head clinical analysis: LEVONEST versus TRI LO ESTARYLLA.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LEVONEST versus TRI LO ESTARYLLA.
LEVONEST vs TRI-LO-ESTARYLLA
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 ethinyl estradiol and norgestimate. Suppresses gonadotropin secretion, primarily FSH and LH, inhibiting ovulation; increases cervical mucus viscosity, impeding sperm penetration; alters endometrial lining, reducing implantation likelihood.
One tablet (levonorgestrel 1.5 mg) orally as a single dose within 72 hours of unprotected intercourse.
One tablet (20 mcg ethinyl estradiol/0.1 mg levonorgestrel) orally once daily for 21 days, followed by 7 days of 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.
Ethinyl estradiol: 19-24 hours (terminal); Norgestimate: active metabolite norelgestromin 28-38 hours; allows once-daily dosing.
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; Fecal: ~30% as metabolites (including ethinyl estradiol conjugates); Biliary: ~20% (enterohepatic recirculation).
Category C
Category C
Oral Contraceptive
Oral Contraceptive