Detailed definition
Prometrium contains bioidentical progesterone milled to small particles ("micronized") to improve oral absorption, suspended in peanut oil. It is FDA-approved for prevention of endometrial hyperplasia in women on estrogen therapy with a uterus, and for secondary amenorrhea. Standard menopause dosing is 100 mg daily continuously combined with daily estrogen, or 200 mg daily for 12 days each month in cyclic regimens. Bedtime dosing leverages the conversion of progesterone to allopregnanolone, which is a positive allosteric modulator of GABA-A receptors and produces a noticeable calming/sleep-promoting effect within 1–2 hours. Generic micronized progesterone is widely available. Vaginal compounded progesterone is an alternative for women who cannot tolerate oral dosing, though it does not produce the same sleep effect because vaginal absorption bypasses the gut/liver allopregnanolone pathway.
Why it matters in menopause
Prometrium is the most commonly prescribed progesterone in modern HRT in the US. It pulls double duty: required for endometrial protection in women on estrogen with a uterus, and a sleep aid through its allopregnanolone metabolite when dosed at bedtime.
Related terms
Sources
External references: Wikipedia.