Alternative dose routes and/or formulations may be a significant consideration for life cycle management. Ex vivo permeability studies with buccal tissues may be used to assess the feasibility of these administration routes, to rank-order compounds in terms of permeability, to optimize formulations, and to assess the extent of drug accumulation in the tissue. Buccal porcine tissues are mounted in Franz cell chambers for permeability evaluation. Test formulations (typically creams or films) are applied to the upper (mucosal) 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) to ensure tissue integrity. The tissue 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.