MICROENCAPSULATION OF KETOPROFEN USING W O/W COMPLEX EMULSION TECHNIQUE/

Sustained release cellulose acetate butyrate (CAB)-polystyrene (PS) mi crocapsules containing ketoprofen (a non-steroidal anti-inflammatory d rug) were prepared adopting the modified W/O/W complex emulsion techni que. The effect of polystyrene concentration and core/coat ratio on th e yield, geometric mean particle diameter, dg, size distribution, drug loading as well as release and surface characteristics of the microca psules was investigated. The results obtained revealed that polystyren e utilization as a wall material plays a dominant role in the manufact uring process. A particular composition of 92.5:7.5 (%) of CAB to PS w as found to improve greatly the microcapsule yield and maximize the dr ug loading. In most cases, the encapsulation efficiencies increased wi th increasing microcapsule size and theoretical drug loading. Kinetic analysis of the data shows that the drug release process from CAB micr ocapsules followed Higuchi model (a diffusion-controlled model for a p lanar matrix), whereas the release behaviour conforms with Baker and L onsdale model (a diffusion-controlled model for a spherical matrix) fo r CAB-PS microcapsules. The preparation of free films of CAB and CAB-P S was described for comparison. The effect of processing parameters (p olystyrene concentration, total polymers concentration and permeant co ncentration) on the permeation of ketoprofen through the polymeric fil ms was discussed. The results demonstrated that ketoprofen permeation through the films and microcapsules could be controlled by modifying t he CAB-PS ratio in the polymer matrices. The permeability constants lo wered with increasing total polymers concentration up to 5% and were p roportional to permeant concentration. To compare the 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 sustained release of the drug (t(0.5); 58-146 h ). Release rates were found to agree with the Baker and Lonsdale model , previously suggested for ketoprofen release from CAB-PS microcapsule s.