Comparative Pharmacology
Head-to-head clinical analysis: LEVONORGESTREL versus NORETHINDRONE AND ETHINYL ESTRADIOL.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LEVONORGESTREL versus NORETHINDRONE AND ETHINYL ESTRADIOL.
LEVONORGESTREL vs NORETHINDRONE AND ETHINYL ESTRADIOL
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Synthetic progestin that suppresses gonadotropin release (GnRH, LH, FSH) via negative feedback on the hypothalamic-pituitary-ovarian axis; inhibits ovulation, thickens cervical mucus, and alters endometrial lining.
Combination estrogen-progestin contraceptive. Suppresses gonadotropin release (FSH, LH) via negative feedback on hypothalamic-pituitary axis, inhibiting ovulation. Thickens cervical mucus to inhibit sperm penetration. Alters endometrium to reduce implantation likelihood.
For emergency contraception: 1.5 mg orally as a single dose or 0.75 mg orally 12 hours apart. For hormonal contraception: 0.03 mg to 0.05 mg orally once daily in combined oral contraceptives; for progestin-only oral contraceptive (mini-pill): 0.03 mg orally once daily. For intrauterine system (IUD): 52 mg intrauterine device inserted for up to 5 years.
One tablet (norethindrone 1 mg / ethinyl estradiol 0.035 mg) orally once daily for 21 days, followed by 7 days of placebo or no tablets.
None Documented
None Documented
Clinical Note
moderateLevonorgestrel + Sulfisoxazole
"The metabolism of Sulfisoxazole can be decreased when combined with Levonorgestrel."
Clinical Note
moderateLevonorgestrel + Erythromycin
"The metabolism of Erythromycin can be decreased when combined with Levonorgestrel."
Clinical Note
moderateLevonorgestrel + Cyclosporine
"The metabolism of Cyclosporine can be decreased when combined with Levonorgestrel."
Clinical Note
moderateLevonorgestrel + Fluconazole
Terminal half-life: 24-30 hours (range 11-45 hours). This prolonged half-life supports once-daily or extended-cycle dosing in contraceptive formulations.
Norethindrone: 6-8 hours (terminal); Ethinyl estradiol: 13-27 hours (terminal, mean ~17 hours). Half-life supports once-daily dosing for contraceptive efficacy.
Renal: 45-60% (metabolites), Fecal: 32-45% (unchanged and metabolites). Biliary excretion contributes to fecal elimination.
Norethindrone: ~50% renal (as metabolites), ~50% fecal (biliary). Ethinyl estradiol: ~40% renal, ~60% fecal (primarily as glucuronide conjugates).
Category C
Category D/X
Progestin
Progestin
"The metabolism of Fluconazole can be decreased when combined with Levonorgestrel."