ABSTRACT
The theory of diffusion has been used in investigating the mechanism of drug transport as well as applied to the design and development of various controlled or sustained release drug delivery systems. This chapter discusses application of the theory of diffusion and dissolution to drug transport and dosage form design. Diffusion is a result of random molecular motion. The partition phenomenon is of paramount importance for the diffusion across skin and other epithelia. Diffusion coefficients can be determined experimentally or calculated using theoretical or empirical models. The diffusion process can be studied by using various methods, such as the permeation method, sorption and desorption kinetics and determination of concentration profile. Scientists in the pharmaceutical industry and practice frequently encounter the principles of diffusion and dissolution. Several sustained and controlled release dosage forms are designed so that the drug release from the dosage form is limited by either diffusion or dissolution.
