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 preparin g a capsule-type controlled release dosage form, in which theophylline (TP) was used as a poorly water-soluble model drug. The TP-loaded unc oated beads were spray-coated with an aqueous ethanolic or ethanolic E C solution, and the drug release characteristics and productivity of e ach product were examined. When the aqueous ethanol was used as the so lvent of the coating solution, a large number of micropores were forme d in the coating, and the porosity of coating and drug release rate co uld be controlled by altering the ethanolic concentration in the coati ng solution. In addition, few agglomerates were produced in the coatin g process, even though there was no anti-agglomeration agent in the co ating solution. The drug release rate from the coated beads could be c hanged by film porosity as well as film thickness. Superposition analy sis revealed that the EC-coated beads with different film porosities o r different coating levels had the same drug release mechanism. It was further found that the drug release behavior of the porous EC film-co ated 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 ph ysiological conditions in the gastrointestinal tract.