Progesterone (Rectal)
Prometrium
Half-life
16 hr
Time to Peak
6 hr
Steady State
~4 days
Bioavailability
50%
Dose Range
100–200 mg
Frequency
Daily
Overview
Micronized progesterone capsules (Prometrium) used rectally -- an off-label route that bypasses first-pass liver metabolism. Achieves 4-6x higher serum progesterone levels than oral at the same dose, with slower absorption and more sustained release. Popularized by Dr. Powers protocol for transfem HRT. Different PK profile from oral: higher bioavailability, later Tmax, less sedation (less allopregnanolone production).
Mechanism of Action
Natural progesterone receptor agonist. Rectal route bypasses hepatic first-pass metabolism, resulting in higher systemic progesterone and lower allopregnanolone levels compared to oral.
Dosing Information
| Route | Dose Range | Half-life | Tmax | Frequency |
|---|---|---|---|---|
| Rectal | 100–200 mg | 16 hr | 6 hr | Daily |
Used in Regimens
1 regimenData Sources
- Peer-reviewed Miles RA et al. Pharmacokinetics of micronized progesterone administered vaginally and rectally
- Peer-reviewed de Lignieres B. Oral micronized progesterone
Related Tools
Track Progesterone (Rectal) with Doseline
Reminders, medication level charts, injection site rotation, and protocol tracking — all free, all private.
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