Progesterone (Oral)
Prometrium · Oral P4
Micronized oral progesterone; short half-life with high first-pass metabolism.
Key takeaways
- FDA-approved for endometrial protection on estrogen therapy; off-label in fertility and feminizing HRT.
- Heavy first-pass metabolism: only ~10% of the dose reaches blood as progesterone itself.
- Sedating metabolite allopregnanolone makes bedtime dosing the standard reported pattern.
- Serum levels stay low even at 200–300 mg, so bloodwork under-represents the clinical effect.
Reported dosing protocols
Protocols reported in research literature and clinic/community use — informational context, not a dosing recommendation.
| Use case | Dose | Route | Frequency | Duration |
|---|---|---|---|---|
| Endometrial protection (label) | 200 mg | Oral | Once daily at bedtime | 12 days per 28-day cycle |
| Continuous HRT (off-label) | 100 mg | Oral | Once daily at bedtime | Ongoing |
Pharmacokinetic summary
- Model tier
- Advanced (t½ + Cmax + Tmax + F)
- Half-life
- 22.8 hours
- Cmax
- 169.53 ng/mL
- Tmax
- 0.1 days
- Bioavailability
- 10%
- Typical dose
- 100–300 mg
Frequently asked questions
Why is oral progesterone taken at bedtime?
First-pass metabolism converts a large share of the dose into allopregnanolone, a sedating neurosteroid. Bedtime dosing turns that drowsiness into a sleep benefit instead of a daytime problem.
Does oral progesterone raise blood progesterone much?
Not much. Only about 10% survives first-pass metabolism, so serum progesterone stays low even at 200–300 mg. Endometrial protection is still achieved, but uses chasing high serum levels usually switch routes.
Is micronized progesterone the same as medroxyprogesterone?
No. Micronized progesterone is bioidentical to human progesterone; medroxyprogesterone acetate (Provera) is a synthetic progestin with a different risk and side-effect profile. The two are not interchangeable.
References
- Dovepress micronized P4 — Multiplier applied to match study graphs.
- Pharmacokinetics of micronized progesterone (DDDT) — Entry's PK source; covers oral and vaginal capsule disposition.
- DailyMed — Prometrium prescribing information — Label dosing for endometrial protection and amenorrhea.
Related compounds
Progesterone (Vaginal)
Vaginal micronized progesterone; bypasses much first-pass metabolism.
Estradiol Topical (EstroGel)
Transdermal estradiol for feminizing HRT. Steady low-level delivery.
Estradiol Cypionate
Injectable estradiol cypionate used in feminizing HRT.
Protocols featuring Progesterone (Oral)
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