The aim of this project is to find an explanation for the variability and differences in oral bioavailability of drugs in veterinary medicine, taking into account differences in drugs dissolution, gastro-intestinal (GI) transit time, GI fluid volume, GI pH, GI permeability and food effects. Therefore, the laboratories of Pharmacology & Toxicology and Pharmaceutical Technology recently started joined research with a PhD student to study the solubility and intestinal permeability of analgesic and non-steroidal anti-inflammatory drugs in the dog, pig, chicken and horse, with the aim to develop a veterinary Biopharmaceutic Classification System (BCS). The Ussing chamber instrument presents a perfect tool to study the intestinal permeability and transport of drugs in these target monogastric animal species.