ABSTRACT
Coated pellets controlling drug release are a very popular dosage form which is widely used in medical practice. At present the coatings of water-insoluble polymers formed from aqueous dispersions are preferred. However, film formation from an aqueous polymeric dispersion is different from that from their organic solutions. A stable film on the pellets surface is produced by coalesces of discrete latex particles at an optimum temperature. The present experimental paper studied the changes of diclofenac sodium dissolution profiles from coated pellets, when their coatings from an aqueous polymeric dispersion of ethyl cellulose were cured for different time periods (1-72 hours) and a temperature of 60 degrees C. Drug release rate was decreasing with the increasing time of the layer curing up to 24 hours. At this time the dissolution curve was similar to a strait line. When the curing time further increased, the drug release was again faster. All prepared samples (with or without seal coat, cured for a period of 24 hour or uncured) were filled into hard gelatine capsules and stored in blisters in three different stability boxes (25 degrees C/60% RH, 30 degrees C/65% RH, 40 degrees C/75% RH) for 6 or 12 months. The best drug dissolution profile and stability were observed for the pellets with the seal coat and ethyl cellulose coating cured for 24 hours.
