Comparative Pharmacology
Head-to-head clinical analysis: LEVONORGESTREL versus PROGESTERONE VAGINAL.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LEVONORGESTREL versus PROGESTERONE VAGINAL.
LEVONORGESTREL vs Progesterone (Vaginal)
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.
Progesterone binds to progesterone receptors in the reproductive tract, converting proliferative endometrium to secretory endometrium, and reduces gonadotropin secretion, inhibiting ovulation.
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.
For progesterone deficiency (e.g., assisted reproductive technology, luteal phase support): 90 mg intravaginally once daily. For secondary amenorrhea: 45 mg intravaginally every other day for up to 12 doses, then 90 mg if needed. For threatened abortion: 200-400 mg intravaginally once or twice daily.
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.
The terminal elimination half-life of progesterone administered vaginally is approximately 5.5 to 6 hours (range: 4.5–8.0 hours) in women with normal renal and hepatic function. This short half-life necessitates twice-daily dosing for sustained effects.
Renal: 45-60% (metabolites), Fecal: 32-45% (unchanged and metabolites). Biliary excretion contributes to fecal elimination.
Primarily hepatic metabolism; about 50-60% of metabolites are excreted renally as glucuronide conjugates, with approximately 30-40% eliminated via feces. Less than 1% of unchanged progesterone is excreted in urine.
Category C
Category A/B
Progestin
Progestin
"The metabolism of Fluconazole can be decreased when combined with Levonorgestrel."