WATER BEHAVIOR DURING DRUG-RELEASE FROM A MATRIX AS OBSERVED USING DIFFERENTIAL SCANNING CALORIMETRY

A solid made from a dissolved mixture of hydroxypropylcellulose and ethylcellulose (SMH) was used as a controlled-release filler, and phenylpropanolamine hydrochloride (PPA) was used as a model drug. With increases in weight fraction of hydroxypropylcellulose (WFH) in the matrix, drug release and water penetration into the matrix decreased. Water behavior during drug release from a SMH matrix was studied by using differential scanning calorimetry (DSC). During the initial stage of dissolution, the water penetrating into the matrix acted as non-freezing water. As the water content of the matrix increased and freezable water was detected at levels that were related to drug release. It was also presumed that before hydrating the whole matrix, water penetrated into the dry portion of the matrix and hydrated the polymer, while further penetrating water did not increase the water content of the hydrated portion, but newly hydrated a dry portion of the matrix.