Membrane diffusion. 3. Influence of solvent composition and permeant solubility on membrane transport.

Abstract Phenomena associated with membrane permeability are important pharmaceutically in drug-transport modeling and in the design of effective drug delivery systems. In the present study, it was found that under certain predetermined conditions the steady-state transfusion of dimethylpolysiloxane membranes by p -amino-acetophenone from binary solvent mixtures was essentially controlled by the thermodynamic activity of the compound in the applied phase. This study augments and supplements present theories concerning drug transport, and it sharply contrasts with previous work where "drug delivery”was maximized at the coincidence of complete solubility and saturation for a fixed ratio of drug and mixed solvent and varying ratio of solvents. Under the conditions of these experiments, specific effects of solvent on mass transport were limited to slight changes in apparent diffusivity, D ′. The D ′ values were calculated from lag times obtained by the Daynes and Barrer extrapolation. Application of these concepts to some practical drug-transport situations is discussed.