Progesterone
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Progesterone (micronized)
Prometrium (oral), Endometrin (vaginal), Crinone (vaginal gel), Prochieve
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Summary
Common uses
Endometrial protection in estrogen-containing HRT0, Secondary amenorrhea0, Luteal support in assisted reproduction0, Preterm birth prevention (vaginal, in selected pregnancies)0
Pharmacy
Starting dose
HRT cyclic: 200 mg PO HS days 1-12 of each month; continuous: 100 mg PO daily; ART luteal support 100 mg vaginal TID or 90 mg gel daily
Preparations
Oral 100, 200 mg capsules (peanut oil; check allergy); 100 mg vaginal insert (Endometrin); 4%, 8% vaginal gel (Crinone); IM 50 mg/mL
US FDA Max
Indication-dependent; 200-400 mg/d oral typical
Pharmacology
Routes
Oral, vaginal, intramuscular
Onset
Sedation/dizziness within hours of oral dose; endometrial effects over days
Duration
Oral: 8-12 hours; vaginal: 24+ hours; IM: days
Half-life
~5-20 hours (oral micronized; highly variable)[1]
Bioavailability
Oral: very low (extensive first-pass); micronization improves uptake somewhat. Vaginal: high local effect with lower systemic levels (first-uterine-pass concentration)[1]
Pregnancy
Vaginal preparations are used in early pregnancy for luteal support and (in selected high-risk patients) for preterm birth prevention. Bioidentical progesterone has reassuring data in pregnancy compared with synthetic progestins.[citation needed]
Legal status
Rx-only in US
Purported mechanism
Micronized progesterone is the bioidentical form of the endogenous hormone; it binds the progesterone receptor (PR-A and PR-B) to drive secretory transformation of estrogen-primed endometrium and supports the maintenance of early pregnancy, and is the structural template for all synthetic progestins.0 Oral progesterone undergoes substantial first-pass to allopregnanolone (a positive allosteric GABA-A modulator), which accounts for the characteristic sedation and dizziness with oral dosing (and the typical HS administration). Vaginal administration provides the "first-uterine-pass effect" — direct uterine delivery with comparatively low systemic levels[1].
References
- ↑ 1.0 1.1 1.2 FDA Prescribing Information, Prometrium (progesterone, USP, micronized), Catalent Pharma, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2015/019781s033lbl.pdf