The effect of crystallization properties and casting solvent on the release of tetracycline from ethyl cellulose films

Abstract

This study was carried out in an attempt to explore the effect of the casting solvent on the crystallization parameters of tetracycline (TC) to be embedded and released from an ethyl cellulose (EC) sustained release delivery system. The mean size and number, the dissolution rate and X-ray diffraction pattern as well as the released amount and rate of release of TC crystals reprecipitated from ethanol: chloroform solutions of various ratios were studied. The casting solvent affected the shape, size and number of TC crystals, influenced their tendency to agglomerate and consequently altered their dissolution rate. X-ray diffraction patterns showed that the casting solvent had no effect on the crystallographic properties of TC crystals. In addition, these properties were not affected by embedding TC crystals in EC film. The changes in the crystallization parameters were reflected in marked differences in the released amount and rate of release of TC from EC films. Films containing TC, cast from solution composition of 50% ethanol: 50% chloroform are superior to those of ethanol or chloroform in their layer ordering, have enhanced release rate and increased released amount of TC. These improved properties are most probably due to the formation of unagglomerated TC particles with small mean size which are uniformly dispersed in the film.