Ex vivo dermal tissue studies are performed with human or porcine skin. The test device is a Franz cell. Test formulations (typically creams or patches) are applied to the upper (external) surface, and samples are removed at pre-determined time points from the reservoir containing buffer that is in contact with the lower (serosal) surface. Reference compounds are either co-dosed if the test compound is in solution or run in parallel if the test compound is in some other type of formulation for quality control. The skin is often extracted at the end of the study to quantify accumulation of the test compound. We can also incubate test formulations with tissue homogenates to assess the metabolic stability of the test compound. Skin studies are used to assess the feasibility of transdermal administration, to rank-order compounds in terms of permeability or accumulation, and to optimize formulations.
In Vivo Dermal Studies
In vivo dermal studies are conducted to evaluate the pharmacokinetics, toxicity, and/or efficacy of test compounds and formulations. Studies may be performed in rodents or non-rodents, on intact or compromised skin, and in healthy or diseased animals. Animal models are selected to most closely mimic the physiology of the human condition.