PLASMA-CONCENTRATIONS OF PROGESTERONE ARE HIGHER IN THE UTERINE ARTERY THAN IN THE RADIAL ARTERY AFTER VAGINAL ADMINISTRATION OF MICRONIZEDPROGESTERONE IN AN OIL-BASED SOLUTION TO POSTMENOPAUSAL WOMEN

Objective: To verify the occurrence of preferential distribution of va ginally administered progesterone to the uterus compared with extrapel vic regions in vivo and in humans. Design: Prospective clinical study. Setting: University medical school. Patient(s): Twenty postmenopausal women undergoing transabdominal hysterectomy for benign pathologies. Intervention(s): Ferry-five minutes before surgery, the women received a single vaginal administration of an oil-based micronized progestero ne (100 mg) solution currently available on the market for IM use. Dur ing the operation, parallel blood samples were drawn from the uterine and radial arteries. Main Outcome Measure(s): Plasma levels of progest erone were measured by RIA. Result(s): Mean (+/-SD) plasma levels of p rogesterone were significantly higher in the uterine artery than in th e radial artery (9.75 +/- 3.21 vs. 5.12 +/- 2.06 ng/mL, respectively). Conclusion(s): Vaginal administration allows a preferential distribut ion of progesterone to the uterus, which confirms the existence of the so-called ''first uterine pass effect.'' (C) 1998 by American Society for Reproductive Medicine.