From the Guidelines
The half-life of oral bioidentical estrogen concentrations is not explicitly stated in the provided evidence, but based on general knowledge, the half-life of oral 17-beta estradiol is approximately 12-24 hours. When considering the administration of oral bioidentical estrogen, it's essential to note that the transdermal route is often preferred due to its ability to mimic physiological serum estradiol concentrations, providing a better safety profile than oral formulations 1. The oral administration of 17β-estradiol, such as 1–2 mg daily, is an option for estrogen replacement in adult women, but it may have a less favorable profile compared to transdermal administration 1.
- Key points to consider when administering oral bioidentical estrogen include:
- Significant first-pass metabolism in the liver, reducing bioavailability
- Higher dosing requirements compared to transdermal or injectable forms
- Importance of consistent daily dosing to maintain therapeutic levels
- Potential for variable pharmacokinetics between individuals based on factors like age, weight, liver function, and concurrent medications
- Need for dose adjustments based on symptom response and hormone level monitoring
- Recommendation to take oral estradiol with food to enhance absorption and reduce gastrointestinal side effects It's crucial to weigh the benefits and drawbacks of oral bioidentical estrogen administration, considering the potential impact on morbidity, mortality, and quality of life, and to prioritize the most recent and highest-quality evidence when making treatment decisions 1.
From the Research
Half-Life of Oral Bioidentical Estrogen Concentrations
- The terminal half-lives for the different estrogen compounds (after oral or intravenous administration) vary from 1-12 hours 2
- The terminal elimination half-life of estradiol was calculated at 16.9 +/- 6.0 h (Test) and 15.0 +/- 4.8 h (Reference) 3
- The terminal elimination half-life of free estrone was calculated at 16.3 h (Test) and 13.5 h (Reference) 3
- The terminal elimination half-life of conjugated estrone was calculated at 11.8 h (Test) and 10.6 h (Reference) 3
Factors Affecting Half-Life
- Oral estrogens have minimal systemic bioavailability (2% to 10%) due to gut and liver (first-pass) metabolism 2
- Smoking decreases achievable estrogen concentrations, and has a greater effect on oral products 2
- Certain medications, such as phenytoin, can increase the metabolism of conjugated estrogens 2
Pharmacokinetics of Bioidentical Estrogen
- Bioidentical compounded hormone therapy is popular among patients, but providers do not have pharmacokinetic information or dosing guidelines for these preparations 4
- The AUC at 24h and at steady-state for estrogens remained consistently lower for all doses of Bi-est tested relative to the patch 4
- Serum levels of estrone, estradiol, estriol, and progesterone were obtained at multiple time intervals during the first 24-h, and at steady-state 4