Comparative Pharmacology
Head-to-head clinical analysis: LEVONEST versus ZOVIA 1 35E 21.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LEVONEST versus ZOVIA 1 35E 21.
LEVONEST vs ZOVIA 1/35E-21
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 estrogen-progestin contraceptive; suppresses gonadotropin release, inhibits ovulation, alters cervical mucus and endometrial lining.
One tablet (levonorgestrel 1.5 mg) orally as a single dose within 72 hours of unprotected intercourse.
One tablet orally once daily at the same time each day for 21 days, followed by 7 placebo tablets (if included in the pack) or a 7-day pill-free interval. Each tablet contains ethinyl estradiol 0.035 mg and norethindrone 1 mg.
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: 5-12 hours (terminal elimination half-life, approximately 8 hours). Ethinyl estradiol: biphasic with terminal half-life of 10-20 hours (mean 15 hours). Clinical context: Steady state reached in 5-7 days.
Renal excretion of conjugated metabolites accounts for approximately 60-80% of an administered dose; fecal elimination via bile accounts for 20-40%.
Renal (approximately 40% as parent drug and metabolites; 20-40% as metabolites; 15-20% as unchanged drug), fecal (30-50% via bile as metabolites), and less than 2% in breast milk.
Category C
Category C
Oral Contraceptive
Oral Contraceptive