Influence of Vehicle of Administration on Intestinal Absorption, Fat Storage, and Biological Activity of Ethynylestradiol (EE) and its 3-Cyclopentyl Ethejr (EEGPE) in Rats

Abstract

Summary When introduced directly into the small intestine of the rat, as oily solutions, ethynylestradiol (EE) or its 3-cyclo-pentyl ether (EECPE) were absorbed much more slowly than when administered as aqueous suspensions. These findings are in agreement with data in the literature on other steroidal compounds. Hydrolysis of the components of sesame oil (dependent upon the presence of bile and pancreatic secretions) seems to be necessary for release and subsequent absorption of EECPE but not EE from the lipid vehicle. Storage in body fat and brain of the unaltered EECPE is increased by its administration as an oily solution instead of an aqueous suspension. The nature of the vehicle of administration, however, had no influence on the degree of biological activity of EECPE as well as EE.