Comparative Pharmacology
Head-to-head clinical analysis: LEVONORGESTREL versus NORETHINDRONE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LEVONORGESTREL versus NORETHINDRONE.
LEVONORGESTREL vs NORETHINDRONE
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 synthetic progestin that binds to progesterone receptors, suppressing gonadotropin (LH and FSH) release from the pituitary, inhibiting ovulation, and inducing secretory changes in the endometrium. It also has weak androgenic and estrogenic activity.
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.
5 mg orally once daily for 5 days starting on day 5 of menstrual cycle or 0.35 mg orally once daily for contraception.
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.
Terminal elimination half-life: 5-14 hours (mean 8-10 hours); clinical context: requires once-daily dosing for steady state after ~2 days (5 half-lives).
Renal: 45-60% (metabolites), Fecal: 32-45% (unchanged and metabolites). Biliary excretion contributes to fecal elimination.
Renal (30-50% as glucuronide conjugates, 5-10% unchanged), fecal (<10%)
Category C
Category D/X
Progestin
Progestin
"The metabolism of Fluconazole can be decreased when combined with Levonorgestrel."