EFFECT OF POLYMER LOADING ON DRUG-RELEASE FROM FILM-COATED IBUPROFEN PELLETS PREPARED BY EXTRUSION-SPHERONIZATION

Many factors are capable of influencing the mechanism of drug release from pellets prepared by extrusion-spheronization. This study was desi gned to elucidate the effect of polymer type and loading and the effec t of processing variables on the rate and mechanism of drug release fr om ibuprofen pellets coated using aqueous polymeric dispersions. Quali tative and quantitative assessment of the success of the film coating process and the quality of the resultant films is made using scanning electron microscopy and in-vitro dissolution testing The importance of plasticizer in polymeric film formation is also discussed. Uncoated p ellets containing 60, 70 and 80% ibuprofen were coated with aqueous po lymeric dispersions of polymethacrylates, ethylcellulose and silicone elastomer films The high drug loading of these pellets adds special in terest to this study. Drug release from uncoated pellets appears to fo llow first-order kinetics. The application of a polymeric membrane to uncoated cores has the effect of retarding drug release. There appears to be a critical coating level below which core coverage by the polym er is incomplete, drug release is diffusion controlled and first-order release kinetics are observed. Above a defined polymer level, drug re lease appears to be membrane controlled and zero-order kinetics are ob served. The presence of plasticizer in the polymeric film imparts a hy drophilic component to an otherwise hydrophobic membrane. This enhance s the penetration of aqueous solvent into the pellet core during in-vi tro dissolution testing increasing the rate of drug release. Scanning electron micrographs reveal the nature of these hydrophilic pores, ben eath which a fine tortuous skeletal network of drug-depleted core is e xposed.