Comparative Pharmacology
Head-to-head clinical analysis: MEGACE versus PROGESTERONE VAGINAL.
Peer-Reviewed Evidence
Head-to-head clinical analysis: MEGACE versus PROGESTERONE VAGINAL.
MEGACE vs Progesterone (Vaginal)
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Megestrol acetate is a synthetic progestin that inhibits pituitary gonadotropin secretion, leading to suppression of ovarian function and reduction of sex hormone levels. It also has antineoplastic effects through interference with estrogen receptor binding and may stimulate appetite via effects on neuropeptide Y and cytokines.
Progesterone binds to progesterone receptors in the reproductive tract, converting proliferative endometrium to secretory endometrium, and reduces gonadotropin secretion, inhibiting ovulation.
Oral: 625 mg (suspension) or 400–800 mg (tablets) once daily.
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
Terminal elimination half-life: 70-95 hours (mean 85 hours) in chronic dosing; shorter in initial doses; clinical context: requires 3-4 weeks to reach steady state.
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.
Primarily renal: ~75% as glucuronide conjugates and unchanged drug; biliary/fecal: ~25% as metabolites.
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