A Study of the Hydrophilic Cellulose Matrix : Effect of Drugs on Swelling Properties

Abstract

The swelling properties of hydrophilic cellulose matrices were studied using three drugs having different water solubility : indomethacin, theophylline, and mannitol. Two swelling parameters : maximum swelling index (V) and the apparent diffusion coefficient of water in the matrix (D_w), were calculated from the swelling data and were used to describe structures and properties of the swollen matrices. The V value indicates the swelling extent as well as the capacity of maintaining the matrix shape, whereas D_w represents the swelling rate that also reflects the structural resistance of the polymer network against the movement of water molecules. The results show that both polymers and incorporated drugs influence the swelling properties of the matrices. Polymers that contain more hydroxypropoxyl group produce matrices with high integrity, even in the presence of drugs. V values indicated that the capacity of the matrices to maintain their shape depends on polymer (i.e., the swelling part). The effect of drug solubility can be seen from D_w values. For a highly water-soluble drug, the structural resistance of the swollen matrices is mainly governed by the drug. In contrast, this primarily influenced by the polymer in the case of drugs that are slightly or poorly water soluble.