The robustness and flexibility of an emulsion solvent evaporation method to prepare pH-responsive microparticles.

A microparticle preparation method based on an emulsion of ethanol in liquid paraffin stabilised using sorbitan sesquioleate which produces enteric microparticles of excellent morphology, size and pH-sensitive drug release was assessed for its robustness to changes in formulation and processing parameters. Prednisolone and methacrylic acid and methyl methacrylate copolymer (Eudragit S) were the drug and polymer of choice. Emulsion solvent evaporation procedures are notoriously sensitive to changes in methodology and so emulsion stirring speed, drug loading, polymer concentration and surfactant (emulsifier) concentration were varied; microparticle size, encapsulation efficiency, yield and in vitro dissolution behaviour were assessed.

Drug distribution in enteric microparticles.

The aim of this study was to assess the distribution of three fluorescent drug or drug-like molecules in enteric microparticles. Microparticles were prepared using the pH-responsive methylmethacrylate polymer Eudragit L by an emulsion solvent evaporation process. In the process drug and polymer are dissolved in ethanol, and dispersed in a liquid paraffin external phase using sorbitan sesquioleate as stabiliser.

Fabrication and in vivo evaluation of highly pH-responsive acrylic microparticles for targeted gastrointestinal delivery.

Acrylic enteric microparticles for oral drug delivery were prepared by an oil-in-oil emulsion solvent evaporation process. The novel use of sorbitan sesquioleate as a surfactant produced Eudragit L55, L and S (pH thresholds of 5.5, 6 and 7, respectively) microparticles of good morphology (spherical, smooth surfaced), size (<100microm) and size uniformity.