POROSITY-CONTROLLED ETHYLCELLULOSE FILM COATING .3. APPLICATION OF POROUS ETHYLCELLULOSE FILM COATING TO CAPSULE-TYPE CONTROLLED-RELEASE PREPARATION OF THEOPHYLLINE

Porous ethylcellulose (EC) film coating technique was used in preparing a capsule-type controlled release dosage form, in which theophylline (TP) was used as a poorly water-soluble model drug. The TP-loaded uncoated beads were spray-coated with an aqueous ethanolic or ethanolic EC solution, and the drug release characteristics and productivity of each product were examined. When the aqueous ethanol was used as the solvent of the coating solution, a large number of micropores were formed in the coating, and the porosity of coating and drug release rate could be controlled by altering the ethanolic concentration in the coating solution. In addition, few agglomerates were produced in the coating process, even though there was no anti-agglomeration agent in the coating solution. The drug release rate from the coated beads could be changed by film porosity as well as film thickness. Superposition analysis revealed that the EC-coated beads with different film porosities or different coating levels had the same drug release mechanism. It was further found that the drug release behavior of the porous EC film-coated beads was not affected by any simulated physiological conditions such as pH, surface tension, ionic strength or paddle rotation speed, indicating that in vivo drug release should not be affected by such physiological conditions in the gastrointestinal tract.