Studies on indomethacin inserts prepared by water-soluble polymers. II. The relation between dissolution rate and...

Inserts containing indomethacin were prepared using water-soluble polymers such as hydroxypropyl cellulose, methylcellulose, hydroxypropyl methylcellulose and polyvinyl alcohol by the film casting method. According to the different characteristics of the polymer used, these inserts exhibit different release kinetics and swelling behaviour. In this study, we examined the relation between swelling behaviour of the polymer and the release of the indomethacin from inserts. Thus an electrical device for measuring the thickness of the hydrated inserts was developed. The thickness of the hydrated inserts was measured by this electrical device at selected time intervals for release studies. The results were interpreted from normalised increases in thickness of the hydrated insert. The mechanism of drug release was identified by means of the value of the ratio R/F, calculated according to the equation developed by Peppas. When the ratio R/F of the insert decreased, drug release from the insert became diffusive. As the normalised thickness of the insert increased, the rate of drug release decreased.