Uterine first pass effect in postmenopausal women

Area of Science:

• Gynecology
• Pharmacology
• Vascular Anatomy

Background:

• Vaginal drug administration preferentially targets the uterus.
• Counter-current transfer between vaginal veins and the uterine artery is a key mechanism.
• The arterial supply to the Fallopian tubes and uterine cornua is debated, impacting vaginal drug delivery efficacy.

Purpose of the Study:

• To investigate the arterial supply to the uterus and Fallopian tubes in postmenopausal women.
• To determine if vaginal drug administration can effectively reach the uterus.
• To provide a rationale for vaginal drug delivery in postmenopausal women.

Main Methods:

• A thermocatheter with four measurement points was endoscopically inserted into the uterine corner in 10 postmenopausal women.
• Temperature changes were recorded during vaginal flushing with room-temperature saline.
• Probe position was re-assessed post-flushing.

Main Results:

• Significant cooling was observed at the lowest measurement point (15 mm from the tip), indicating localized cold transfer.
• Temperature reduction was significantly greater at the lowest point compared to others.
• This cooling effect was attributed to local transfer from vaginal vein blood to uterine arterial blood, not the ovarian artery.

Conclusions:

• The uterine artery primarily supplies the uterus in postmenopausal women.
• The corneal part of the uterine cavity receives supply from the ovarian artery.
• Vaginal drug administration is a viable strategy for achieving local effects in the postmenopausal uterus.