Micronized ethylcellulose used for designing a directly compressed time-controlled disintegration tablet

Ethylcellulose (EC) of varying particle sizes has been used as an outer coa ting layer to design a novel dry-coated tablet with rime-controlled drug re lease. This dry-coated tablet, containing a core tablet of sodium diclofena c and an outer coating layer of EC, was prepared by direct compression. The drug release from dry-coated tablet exhibited an initial lag period that w as dependent on the particle size of the EC powder, followed by a stage of rapid drug release. The smaller the EC particle size used the longer the la g time obtained, suggesting the particle size of EC powder could modulate t he timing of drug release from such a dry-coated tablet. The period of the lag time for sodium diclofenac released from dry-coated tablets was correla ted with the penetration distance of the solvent into dry-coated tablet by an in vitro dye penetration study. The densest packing of EC powders appear ed on the upper and lower surfaces of dry-coated tablet after compression, resulting in a tight structure yielding a slower penetration of the solvent . Whereas loose packing of EC powders occurred in the middle of the lateral surface of dry-coated tablet, this loosely packed surface readily allowed solvent penetration and that finally caused the splitting of tablet shell i nto two halves in the dissolution medium. The results suggest that these dr y-coated tablets prepared with different particle sizes of EC powder as an outer coating layer might offer a desirable release profile for drug delive ry at the predetermined times and/or sites. (C) 2001 Elsevier Science B.V. All rights reserved.