In vitro release kinetics of Tolmetin from tabletted Eudragit microparticles

In a previous paper the preparation has been described, by three different techniques, of microparticles made of Eudragit((R)) RS 100 and RL 100 conta ining a NSAI agent, Tolmetin. Freely flowing microparticles failed to affec t significantly the in vitro drug release, which displayed a similar dissol ution profile after micro-encapsulation to the free drug powder. Microparti cles were then converted into tablets and the effect of compression on drug deliver, as well as that of the presence of co-additives, was studied in t he present work. Furthermore, microparticles were also prepared by adding M gO to the polymer matrix, to reduce the sensitivity of the drug to pH chang es during its dissolution. Similarly, magnesium stearate was also used for microparticle formation as a droplet stabilizer, in order to reduce particl e size and hinder rapid drug release. A mathematical evaluation, by using t wo semi-empirical equations, was applied to evaluate the influence of disso lution and diffusion phenomena upon drug release from microparticle tablets .