Equivalent Oral Estradiol Dosing for 0.05mg Patch
When transitioning from a 0.05mg (50 μg/day) estradiol patch to oral estradiol, start with 1-2mg oral estradiol daily, recognizing that oral administration requires significantly higher doses due to extensive first-pass hepatic metabolism. 1
Dosing Conversion Rationale
Why Oral Doses Are Much Higher
Oral estradiol undergoes extensive first-pass metabolism in the liver, converting most estradiol to estrone before reaching systemic circulation, requiring milligram doses (1000-2000 μg) to achieve the same effect as 50 μg transdermal delivery 2, 3
Transdermal patches deliver estradiol directly into systemic circulation without hepatic metabolism, maintaining physiological estradiol plasma levels of 35-100 pg/mL with just 50 μg daily 2, 4
The conversion ratio is approximately 20-40:1 (oral to transdermal), meaning a 50 μg patch requires 1-2mg oral estradiol to achieve comparable serum levels 3, 4
Recommended Oral Conversion
Start with 1mg oral micronized estradiol daily and titrate based on symptom control and serum estradiol levels, targeting 35-100 pg/mL 2
If symptoms persist, increase to 2mg daily, which is the standard oral dose used in most clinical trials and equivalent to the 50 μg patch 1, 5
Avoid exceeding 2mg daily initially, as higher doses provide no additional benefit and increase adverse effects 1
Critical Progestin Requirements
For Women With Intact Uterus
You must add progestin to reduce endometrial cancer risk, regardless of estrogen route 1, 6
Use micronized progesterone 200mg daily for 12-14 days every 28 days in a sequential regimen 1, 6
Alternative: medroxyprogesterone acetate 10mg daily for 12-14 days per month 1
For continuous regimens: use norethisterone 1mg daily, MPA 2.5mg daily, or dydrogesterone 5mg daily 1
Common Pitfalls to Avoid
Do not use a 1:1 microgram conversion (i.e., 50 μg oral = 50 μg patch) as this severely underdoses patients due to first-pass metabolism 2, 3
Do not start with high oral doses (>2mg) without first trying lower doses, as the ACOG recommends using the lowest effective dose 1
Do not forget progestin supplementation in women with an intact uterus, as unopposed estrogen significantly increases endometrial cancer risk 1, 6
Monitor serum estradiol levels 2-4 weeks after conversion to ensure therapeutic range of 35-100 pg/mL is achieved 2