Estradiol Undecylate

Estradiol HRT IM Published Clinical Data

Half-life

20.8 days

Time to Peak

7 days

Steady State

~105 days

Bioavailability

100%

Dose Range

5–20 mg

Frequency

Every 2 weeks

Overview

Very long-acting injectable estrogen ester with limited commercial availability. The long undecylate ester chain produces an extremely slow absorption and elimination profile, allowing extended dosing intervals of 2-4 weeks.

Mechanism of Action

Prodrug: undecylate ester is hydrolyzed in vivo, releasing active 17β-estradiol.

Dosing Information

Route	Dose Range	Half-life	Tmax	Frequency
Intramuscular (IM)	5–20 mg	20.8 days	7 days	Every 2 weeks, Every 4 weeks

Storage & Handling

Room temperature — Limited commercial availability. Primarily from compounding pharmacies.

Used in Regimens

Estradiol Undecylate is not currently part of any catalog regimen.

Data Sources

Community estrannaise.js — EUn IM and EUn SubQ PK models
meta analysis Transfeminine Science — Informal Meta-Analysis of Estradiol Curves

Related Tools

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