What is the dose equivalent to 1 milligram (mg) of estradiol (oral) in a topical gel formulation?

From the Guidelines

The dose equivalent to 1mg estradiol PO in topical gel is approximately 0.5 to 1 mg daily, as indicated by the doses ranging from 0.5 to 1 mg daily of vaginal gel administration of 17βE in the study 1. When considering the conversion from oral to topical estradiol, it's essential to note that topical administration bypasses first-pass liver metabolism, potentially leading to more stable blood levels and fewer side effects.

• Key points to consider when using topical estradiol gel include:
  • Application to clean, dry skin, typically on the arms, shoulders, or thighs, rotating application sites to prevent skin irritation
  • Allowing the gel to dry completely before dressing
  • Washing hands thoroughly after application to prevent unintended transfer
• The study 1 provides guidance on hormonal replacement therapy in adolescents and young women with chemo- or radio-induced premature ovarian insufficiency, including recommendations for transdermal and vaginal gel administration of 17βE.
• It's crucial to adjust the dose of 17βE according to each woman's tolerance and feeling of wellbeing, as stated in the study 1.
• Monitoring symptoms and hormone levels after switching formulations is recommended to ensure therapeutic efficacy, considering individual responses may vary.

From the Research

Dose Equivalent of 1mg Estradiol PO in Topical Gel

The dose equivalent of 1mg estradiol PO in topical gel is not directly stated in the provided studies. However, some studies provide information on the bioavailability and dosage of estradiol in different forms:

• The study 2 compared the bioavailability of oestradiol from a gel, a patch, and a tablet. It found that the bioavailability of oestradiol from the gel was 61% as compared with the tablet.
• The study 2 also stated that 1.5 mg oestradiol as a transdermal gel yielded similar serum oestradiol profiles with a peak concentration 4-5 h after administration, compared to a 2 mg oestradiol valerate tablet.
• No direct conversion factor is provided in the studies to determine the exact dose equivalent of 1mg estradiol PO in topical gel.

Key Points

• The bioavailability of estradiol from a transdermal gel is 61% compared to a tablet 2.
• A dose of 1.5 mg oestradiol as a transdermal gel has a similar serum oestradiol profile to a 2 mg oestradiol valerate tablet 2.
• There is no direct information available to determine the dose equivalent of 1mg estradiol PO in topical gel.