Comparative Pharmacology
Head-to-head clinical analysis: LEVONORGESTREL versus NORETHINDRONE AND ETHINYL ESTRADIOL AND FERROUS FUMARATE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LEVONORGESTREL versus NORETHINDRONE AND ETHINYL ESTRADIOL AND FERROUS FUMARATE.
LEVONORGESTREL vs NORETHINDRONE AND ETHINYL ESTRADIOL AND FERROUS FUMARATE
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.
Norethindrone is a progestin that suppresses gonadotropin release, inhibiting ovulation. Ethinyl estradiol is an estrogen that provides negative feedback on the hypothalamic-pituitary axis, further suppressing ovulation and altering cervical mucus and endometrial lining. Ferrous fumarate is an iron supplement for replacement of menstrual iron loss.
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 10 mcg, and ferrous fumarate 75 mg) orally once daily at the same time each day for 28 consecutive days, starting on day 1 of menstrual cycle.
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
None Documented
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: 5-8 hours (terminal). Ethinyl estradiol: 13-27 hours (terminal). Clinical context: dosing interval is 24 hours based on ethinyl estradiol half-life.
Renal: 45-60% (metabolites), Fecal: 32-45% (unchanged and metabolites). Biliary excretion contributes to fecal elimination.
Norethindrone: ~80% renal (as glucuronide and sulfate conjugates), ~20% fecal. Ethinyl estradiol: ~40% renal, ~60% fecal via enterohepatic recirculation. Ferrous fumarate: iron is absorbed and incorporated; excess excreted in feces as unabsorbed.
Category C
Category D/X
Progestin
Progestin
"The metabolism of Fluconazole can be decreased when combined with Levonorgestrel."