Estradiol Oral
Estrace
Half-life
16.5 hr
Time to Peak
6 hr
Steady State
~4 days
Bioavailability
5%
Dose Range
1–8 mg
Frequency
Daily
Overview
The most commonly prescribed form of estradiol globally. Swallowed micronized estradiol tablets undergo extensive first-pass hepatic metabolism, converting most E2 to estrone (E1). Results in high E1:E2 ratio (5:1 to 14:1). Elevated VTE risk compared to non-oral routes due to first-pass liver stimulation. Generally not sufficient alone for testosterone suppression without anti-androgen.
Mechanism of Action
Micronized 17β-estradiol absorbed from GI tract and undergoes extensive first-pass hepatic metabolism. Converted largely to estrone (E1) and estrone sulfate (E1S). Stimulates hepatic protein synthesis (SHBG, clotting factors, triglycerides).
Dosing Information
| Route | Dose Range | Half-life | Tmax | Frequency |
|---|---|---|---|---|
| Oral | 1–8 mg | 16.5 hr | 6 hr | Daily, Twice daily |
Storage & Handling
Room temperature — Standard micronized estradiol tablets. Store at 20-25°C.
Used in Regimens
3 regimensOral E2 + Spironolactone
Oral estradiol with spironolactone anti-androgen — the most commonly prescribed transfeminine HRT regimen in North America. Simple, accessible via GP or Planned Parenthood informed consent. Higher VTE risk than transdermal routes due to first-pass hepatic metabolism.
Oral estradiol 2–6mg/day in divided doses.
Sublingual E2 + Spironolactone
Sublingual estradiol tablets dissolved under the tongue — bypasses first-pass hepatic metabolism, producing sharp peaks followed by rapid decline. Lower VTE risk than oral. Requires 3–4 daily doses for stable levels. Popular in the US/Canada community.
Sublingual estradiol 2–8mg/day in divided doses (3–4x daily).
Patch + Sublingual E2 Combination
Transdermal patches as base estrogen delivery with sublingual estradiol tablets supplementing to reach T-suppression levels. Patches provide the lowest VTE risk of all estradiol routes but may not achieve high enough levels for monotherapy T-suppression. A middle-ground between safety (transdermal) and efficacy (injectable).
1–2mg sublingual if patch levels insufficient on bloods.
Data Sources
- FDA Label Estrace (estradiol tablets) — FDA Prescribing Information
- Peer-reviewed Kuhl 2005 — Pharmacology of estrogens and progestogens
Related Tools
Track Estradiol Oral with Doseline
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