Permeability enhancement methods

For example, the permeability coefficients of intact stratum corneum for lipophilic compounds such as corticosterone are in the order of 2 x lO cm/sec in an aqueous system. The aqueous solubility of corticosterone is approximately 0.3mg/mL.f A simple calculation using Eqs. (1) and (2) show why only potent drug of a required dose less than 1 mg per day can utilize the transdermal route via passive delivery. Physical and chemical transdermal enhancers are required for most drugs. Table 1 provides a list of transdermal enhancement methods and companies involved in the development of technologies related to these methods. The readers are encouraged to view the company websites listed in the table, but caution must be taken because the information and claims provided in a company website are subjective and not peer-reviewed. 

Marquis [86] described a method of enhancing the permeability profile of an oil-bearing formation during the injection of a foam-forming composition or a... 

Pulsed electric field is another alternative to conventional methods of extraction. PEF enhances mass transfer rates using an external electrical field, which results in an electric potential across the membranes of matrix cells that minimizes thermal degradation and changes textural properties. PEF has been considered as a nonthermal pretreatment stage used to increase the extraction efficiency, increasing also permeability throughout the cell membranes. 

The ex vivo methods lend themselves easily for the performance of mechanistic investigations. In order to optimize selection of drug candidates prior to further clinical development, it is important to decipher the contributive roles of permeation, metabolism, efflux, and toxicity. This will then make it possible to properly channel the optimization process, for instance, by permeation enhancement, mucoadhesion, modification of the physicochemical characteristics of the drug, or even change in the route of administration in case the drug and/or formulation turns out to be too toxic. Regarding permeability studies, it is possible not only to quantify passive diffusion but also to identify and characterize (compound)-specific carrier-mediated transport routes. These tools have been used to identify and characterize the relative contribution of... 

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