Comparative Pharmacology
Head-to-head clinical analysis: LYBREL versus TRIPHASIL 28.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LYBREL versus TRIPHASIL 28.
LYBREL vs TRIPHASIL-28
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Combination of levonorgestrel and ethinyl estradiol: suppression of gonadotropins (FSH and LH) via negative feedback, inhibiting ovulation; thickening of cervical mucus to impede sperm penetration; alteration of endometrium to reduce implantation likelihood.
Combination estrogen-progestin contraceptive; suppresses gonadotropin secretion, inhibits ovulation, alters cervical mucus and endometrium.
One tablet (levonorgestrel 0.1 mg/ethinyl estradiol 0.02 mg) orally once daily for 21 days, followed by 7 placebo tablets for 28-day cycle.
1 tablet orally once daily for 28 days; each tablet contains levonorgestrel 0.050 mg and ethinyl estradiol 0.030 mg (6 days), levonorgestrel 0.075 mg and ethinyl estradiol 0.040 mg (5 days), levonorgestrel 0.125 mg and ethinyl estradiol 0.030 mg (10 days), followed by 7 inert tablets. The first dose is taken on the first Sunday after onset of menstruation or on day 1 of the menstrual cycle.
None Documented
None Documented
Terminal elimination half-life: 27 ± 8 hours; requires ~5 days to reach steady-state; clinical significance: missed doses lead to rapid loss of contraceptive efficacy.
Levonorgestrel: terminal half-life 11-45 hours (mean 24-30 h); Ethinyl estradiol: terminal half-life 10-27 hours (mean 17 h). Steady-state reached after 5-7 days.
Renal: 50-60% as metabolites, ~20% as parent drug; fecal: 30-40%; biliary: 10-20%.
Renal (about 50-60% as metabolites, <10% unchanged), fecal (about 30-40% via biliary elimination). Ethinyl estradiol undergoes enterohepatic recirculation.
Category C
Category C
Oral Contraceptive
Oral Contraceptive