Perorally administered quaternary ammonium compounds are well accepted therapeutics for the treatment of hypotension and bradycardia, as well as biliary, gastrointestinal and urinary-tract spasms. Most of these permanently charged compounds have been reported to show low intestinal absorption rates and thus low bioavailabilities after peroral administration. This observation has been predominantly related to the hydrophilic nature of the compounds resulting in difficulties overcoming the lipophilic barrier of the intestinal epithelium. However, few quaternary ammonium compounds are known to be well absorbed by the intestine and intestinal transport proteins have been hypothesized to contribute to the differences in the intestinal permeation of the drugs. Annette Koggel investigates the influence of Organic Cation Transporters (OCT`s) and the multidrug resistance transporter P-glycoprotein (P-gp) on the epithelial permeability of cationic drugs by using cell-culture based in vitro transport- and radioligand binding methods. On the basis of her results new insights into the intestinal absorption and excretion of cationic drugs could be won. The authoress: born in 1970; studied Pharmacy at the Johannes Gutenberg-University in Mainz; qualified as a pharmacist; PhD studies under the supervision of Prof. Dr. P. Langguth; Annette Koggel works as a research associate in the department of biopharmacy and pharmaceutical technology at Johannes Gutenberg-University School of Pharmacy in Mainz.