Studying the Effect of Dispersed Drug Crystal in the Organic Phase on the Encapsulation by Solvent Evaporation Technique; (4) Dependent models as tools for studying the drug release
Different dependent models (kinetics and mechanisms) were used to study the Aspirin release from different particle size ranges of Eudragit RS100 microcapsules prepared with the same or different theoretical drug content in relation to the method of drug entrapment. The drug release kinetic obeys zero order kinetic and Higuchi model. Higuchi model had a large application in the polymeric matrix systems but zero order is an ideal to coated dosage forms. Both two forms are found to be the structure of Eudragit RS100 microcapsules entrapped drug. The good fitting of the drug release to Korsmeyer-Peppas model, which can be used as a decision parameter between the above two models, indicates the mechanism of the drug release in every case is either Case II or supper Case II. The above results are also supported by the good fitting of the dissolution data to Hixson-Crowel model since Eudragit RS100 is a swellable and non soluble polymer. The application of Weibull model again support the above results since the value of b ˃ 1 in every case which indicating that the drug release mechanism is case II. Application of first order equation to the whole release data showed no fitting but the graphic representation showed bi-phase release data with one point transition time between the two phases which is after 2 hrs. There is no good fitting between Baker-Lansodale model and drug release data in every case but good fitting in every case was found with Hopfenberg model.
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