Intravaginal administration of progesterone: the first uterine pass effect

Abstract

The author reviews the effects of intravaginal progesterone on the endometrium. Va ginaUy administered progesterone achieves adequate endometrial secretory transformation, despite serum progesterone leveis lower than those observed after intramuscular administration; this fact can be explained by the fi rst uterine pass effect. The author concludes that intravaginal route of administration is safe and effective for support of the luteal phase in assisted reproductive techniques, and observes that the sustained-release vaginal gel of progesterone has the advantage of being administered as a once daily application.