INFLUENCE OF DIFFERENT-SHAPED PIGMENTS AND PLASTICIZERS ON THEOPHYLLINE RELEASE FROM EUDRAGIT RS30D AND AQUACOAT ECD30 COATED PELLETS

The release properties of theophyline pellets coated with Eudragit RS3 0D and Aquacoat ECD30 containing different types of pigments and plast icizers were investigated. The pigments used were titanium dioxide, re d iron oxide, talc, mica or platelet-shaped pearl luster pigments with either titanium dioxide or-iron oxide surfaces. Dibutyl phthalate or triethyl citrate were applied as plasticizers. Small-scale trials were not with commercially available theophylline pellets coated in a mini ature fluid-bed pan coater. Dissolution tests showed that drug release depended mostly on the particle shape and size of the pigments. The p olarity of the surface of the pigment was of minor influence. With the exception of red iron oxide and titanium dioxide, which at higher con centrations could not be distributed within the film homogeneously inc reasing pigment content led to decreasing dissolution rates. In additi on, drug release was found to be related to the stirring time of the p lasticized mixtures before spraying.