Polymer erosion of hydrophilic matrices

摘要

Hydroxypropylmethylcellulose (HPMC) is widely used in controlled release dosage forms as the rate controlling polymer. An important characteristic for controlled release polymers is to hydrate quickly to form a protective gel barrier. As water diffuses into the matrix, the polymer concentration in the hydrated layers decreases over time. The outemost layer of the matrix eventually becomes diluted to the point where individual chains detach from the matrix and diffuse into the bulk solution. The polymer chains begin to disentangle at the surface once the polymer concentration is diluted below a critical polymer concentration, resulting in surface erosion from the matrix. The purpose of this study was to examine the polymer erosion of matrices in deionized water comprised of various HPMC viscosity grades with the same substitution composition.