Effects of ethanol on intestinal absorption of drugs: In situ studies withciprofloxacin analogs in acute and chronic alcohol-fed rats

Background: Previous work from our laboratory on the effect, in rats, of ch ronic ethanol intake on the intestinal absorption of ciprofloxacin analogs suggested an increased polarity of the lipoidal membrane constituents witho ut effects on the aqueous environment. The aim of the present study was to investigate the influence of acute ethanol intake on the absorption of the same series of compounds. Methods: The effects of in situ ethanol exposure on intestinal absorption w ere determined in rats fed either a standard liquid diet or a 5% (w/v) etha nol-containing liquid diet. Acute intestinal exposure to 5% (w/v) ethanol w as performed in situ in each feeding group. The biophysical absorption mode l was used to establish correlations between the actual absorption rare con stants, and the lipophilicity indexes, for each group of rats. Results: Acute exposure to ethanol produces an increase only in the absorpt ion of hydrophilic homologs in both control and chronic ethanol fed groups. This suggests the absence of homeoviscous adaptation of the intestinal mem brane. The biophysical model used allows us to discriminate between the eff ects of acute and chronic ethanol treatment on the intestinal membrane. Conclusions: These results suggest that in contrast to previous; reports ch ronic ethanol treatment increases membrane polarity and acute alcohol intak e appears to modify membrane fluidity.