Influence of route of administration on progesterone metabolism.

Compared progesterone plasma concentrations in a randomized cross-over study after po and vaginal administration of progesterone in 9 healthy premenopausal women. After po administration, 5α-pregnanolone levels were even higher than those of progesterone, and 5β-pregnanolone levels were similar to those of progesterone. By contrast, after vaginal administration, only a small increase in 5α-pregnanolone was observed, and 5β-pregnanolone levels were not significantly affected. Results strongly support the concept that progesterone activities on the central nervous system can be modulated by the route of administration. (PsycINFO Database Record (c) 2016 APA, all rights reserved)