[Lipophilicity and enteral absorption of cardenolides (author's transl)]

Intestinal absorption of 15 cardenolides has been examined in cats. The 3H-labelled substances were injected intraluminally into ligated duodenal loops of anaesthetized animals. 3H-Concentrations were followed in the portal circulation and in the bile. 1 h after drug administration the duodenal sac was removed, and the residual in the lumen then was washed out and assayed radiochemically. The decrease of radioactivity during 1 h was calculated as extent of absorption (QR). Cardenolide absorption was compared with the corresponding in vitro parameters of lipophilicity like octanol/water partition coefficients and Rm values from reversed phase thin-layer chromatography. The Spearman rank sum correlation test revealed coefficients of 0.95 to 0.97. The result lends support to the use of the easily available Rm values as a good tool to predict intestinal absorption of various cardenolides.