Comparative Pharmacology
Head-to-head clinical analysis: MEGACE versus PROMETRIUM.
Peer-Reviewed Evidence
Head-to-head clinical analysis: MEGACE versus PROMETRIUM.
MEGACE vs PROMETRIUM
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 target tissues, promoting endometrial maturation, reducing uterine contractility, and suppressing ovulation.
Oral: 625 mg (suspension) or 400–800 mg (tablets) once daily.
Oral: 200 mg once daily at bedtime for 12 consecutive days per 28-day cycle in combination with conjugated estrogens 0.625 mg daily. For secondary amenorrhea: 400 mg once daily at bedtime for 10 days. Intravaginal: 4% gel (90 mg) or 8% gel (180 mg) applied every other day for 6 doses in postmenopausal women with intact uterus on estrogen therapy.
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.
Terminal half-life: Approximately 16-18 hours for oral micronized progesterone (Prometrium); permits twice-daily dosing for luteal phase support.
Primarily renal: ~75% as glucuronide conjugates and unchanged drug; biliary/fecal: ~25% as metabolites.
Urine (50-60% as metabolites, <1% unchanged); feces (20-30% as metabolites); minor biliary elimination.
Category C
Category C
Progestin
Progestin