Controlled release of human immunoglobulin G. 1. Release kinetics studies.

The release of human immunoglobulin G (IgG) using ethylene-vinyl acetate copolymer (EVAc) as a polymer carrier was studied by fabricating them into two commercially available dosage forms: slab and microsphere. A first-order flux decay model and two hierarchical models concerned with the mass transfer coefficient on the slab surface were used to describe the mechanism of release kinetics and the results compared. These models gave insight to some of the important physical parameters of drug release such as the diffusion coefficient, time constant of release, and initial flux. It was found that the release mechanism varies with time, and hence no single model can be used to predict the release profile for the entire period of study. A controlled release study by matrix coating was also done. The results obtained were utilized to examine the suitability of a particular dosage form (matrix geometry) of IgG for clinical applications. The release data compared with the standard methods of IgG therapy proves localized drug delivery to be a major boon for immunodeficient patients.