Sustained release cellulose acetate butyrate (CAB) – polystyrene (PS) microcapsules containing Ketoprofen (a non steroidal anti-inflammatory drug) were prepared adopting the modified W/O/W complex emulsion technique. The effect of polystyrene concentration and core/coat ratio on the yield. geometric mean particle diameter dg, size distribution, drug loading as well as release and surface characteristics of the microcapsules were investigated. The results obtained revealed that polystyrene utilization as a wall material play a dominant role to the manufacturing process. A particular composition of 92.5:7.5 (percent) of CAB to PS was found to improve greatly the microcapsule yield and maximize the drug loading. In most of cases, the encapsulation efficiencies increased with increasing microcapsule size and theoretical drug loading. Kinetic analysis of the data shows that the drug release process from CAB microcapsules followed Higuchi model (a diffusion-controlled model for planar matrix), whereas the release behavior actually conforms with Baker and Lonsdale model (a diffusion-controlled model for spherical matrix) for CAB - PS microcapsules. The preparation of free films of CAB and CAB-PS was described for comparison. The effect of processing parameters (polystyrene concentration, total polymers concentration and permeant concentration) on the permeation of ketoprofen through the polymeric films was discussed. The results demonstrated that ketoprofen permeation through the films and microcapsules could be controlled by modifying the CAB-PS ratio in the polymer matrices. The permeability constants decreased with increasing the total polymers concentration up to 5 percent and were proportional to permeant concentration.
To compare kinetics of drug release from' polymeric films with those of microcapsules, ketoprofen was incorporated at different concentrations within CAB-PS cast films. These films exhibited timed release of the drug (t0,5; 58.22-146.46 hr), Release rates were found to agree with Baker and Lonsdale model, previously suggested for ketoprofen release from CAB-PS microcapsules. In conclusion: to expedite successfully the microencapsulation process, cast films were prepared to examine the build- up and permeability characteristics of the membrane coat structure. The surface characteristics of the prepared microcapsules were found to explain precisely the release profiles.