Monodisperse albumin microspheres were successfully prepared by both chemical or thermal hardening methods via membrane emulsification using microporous glass membranes with uniform pore sizes. The monodispersity of the microspheres was found to depend strongly on parameters such as albumin concentration, emulsifier concentration, and volume ratio of the internal aqueous phase (albumin solution) to the dispersion medium (organic solvent). The optimum conditions for obtaining monodisperse albumin microspheres are described.

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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 was investigated. The results obtained revealed that polystyrene utilization as a wall material plays a dominant role in the manufacturing process. A particular composition of 92 center dot 5: 7 center dot 5 (%) of CAB to PS was found to improve greatly the microcapsule yield and maximize the drug loading. In most 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 a planar matrix), whereas the release behaviour conforms with Baker and Lonsdale model (a diffusion-controlled model for a 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 lowered with increasing total polymers concentration up to 5% and were proportional 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 (t0 center dot 5; 58-146 h). Release rates were found to agree with the Baker and Lonsdale model, previously suggested for ketoprofen release from CAB-PS microcapsules.

This study was undertaken to develop a sustained-release formulation of tiaramide (TAM), a non-steroidal anti-inflammatory drug with a short half-life, using alginate of different chemical compositions. Alginate gel beads containing TAM were prepared using a gelation of alginate with calcium cations. Bead performance was evaluated in vitro for different dissolution media and beads were also subjected to coating. TAM release was dependent both on its solubility in dissolution medium and the guluronate residue content of the alginate used. The release rate was in the following order: in pH 1.2 > pH 6.8 > water. The fast release rate in pH 1.2 is the result of the high solubility of TAM in acidic medium. Beads based on alginate rich in guluronate residue had the lowest release rate, which can be attributed to the compact structure formed by guluronate residues through cooperative interaction with calcium ions. Alginate beads were administered to beagle dogs, and pharmacokinetic parameters (mean residence time [MRT], tmax, Cmax, and AUC) were calculated. In vivo results were in good agreement with in vitro dissolution characteristics. Beads with high guluronate content gave the best controlled results. In addition, coated beads showed a more satisfactory sustained-release pattern. Calcium alginate appears to be a potential carrier for controlling drug release rate, even for water-soluble drugs such as TAM.

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