The Comparability of In Vitro and Ex Vivo Studies on the Percutaneous Permeation of Topical Formulations Containing Ibuprofen
Jessica Stahl, Bettina Blume, Silvia Bienas and Manfred Kietzmann
In order to avoid in vivo experiments and to gain information about the suitability of surrogates for skin replacement, Franz-type diffusion cell experiments were conducted by using three ibuprofencontaining formulations (cream, gel and microgel) on bovine split-skin samples and cellophane membranes. Moreover, ex vivo examinations were performed on the isolated perfused bovine udder, to study the comparability of in vitro and ex vivo experimental set-ups. Depending on the formulation, noticeable differences in the permeation of Ibuprofen occurred in vitro (udder skin) and ex vivo (isolated perfused bovine udder), but not in the cellophane membrane. The rates of ibuprofen permeability (cream > gel > microgel) and adsorption into the skin (gel > microgel > cream) varied with the formulation, and were probably caused by differences in the ingredients. Furthermore, different storage conditions and seasonal variation in the collection of the skin samples probably led to differences in the amounts of ibuprofen adsorption apparent in the isolated bovine udder and udder skin. In vitro diffusion experiments should be preferred to experiments on isolated organs with regard to the costs involved, the throughput, and the intensity of labour required, unless metabolism of the drug in the skin, or cell–cell interactions are of particular interest.