Influence of preparation conditions on the properties of Eudragit microspheres produced by a double emulsion method

Abstract

The aim of the present work was to study the preparation and characteristics of sustainedrelease microspheres. As a model drug, sodium diclofenac was encapsulated in microspheres of the polymer Eudragit RS by using a double emulsion-solvent evaporation method. Investigations were carried out on the effects of the preparation method, the rate of the first step of emulsification, and the phase volume and composition (drug and additives) on the physical parameters of the product: its drug encapsulation, and the drug release. We evaluated the resulting microsphere structure [by differential scanning calorimetry (DSC)], the particle size, the surface area (by scanning electron microscopy), the entrapment and encapsulation efficiency (applying a novel method, energy-dispersive x-ray fluorescence analysis), the viscosity of the primary emulsion, and the organic solvent residue (by gas chromatography). We also evaluated and compared the samples by means of the kinetic data relating to drug release. The particle size could be decreased to one third by increasing the external aqueous phase ratio. In the first step of emulsification, elevation of the stirring rate led to microspheres with unfavorable characteristics. Increase of the active agent content and the plasticizer concentration had opposite effects. We applied a covalently not bound plasticizer, which was shown to influence the structure of the microspheres considerably. Drug Dev. Res. 64:41-54, 2005.

Development of spray‐ and freeze‐dried high‐concentration sesamol emulsions and antioxidant evaluation in fibroblasts and UV‐exposed rat skin slices

“…Because preparation conditions can strongly influence the activity of encapsulated drugs [Sipos et al, 2005;Harris et al, 2004], we evaluated the influence of FD and SD at different temperatures on the main physicochemical characteristics (droplet size distribution, residual moisture, crystallization, and microscopic structure) of the new dry SEOH emulsions. In addition, their antioxidant and free radical scavenging capacity were determined using electron spin resonance (ESR) and spectrophotometrical tests either in media of different lipophilicities, or in two models widely used in pharmacological and dermatology research, i.e., cultured murine fibroblasts and UVirradiated rat skin, respectively.…”

Investigation on Processing Variables for the Preparation of Fluconazole-Loaded Ethyl Cellulose Microspheres by Modified Multiple Emulsion Technique

“…Unlike w/o emulsification method, water-in-oil-in-water (w/o/w) emulsion solvent evaporation technique proves much more effective when the aqueous solubility of drug is high (>900 mg/ml) and partitioning into the organic phase is disfavorable (6). Accordingly, microspheres containing water soluble drugs have been prepared using different polymers such as poly(lactide-co-glycolide) (PLGA) (7), eudragit RS (8), polymethyl methacrylate (9). In addition, modified procedures of this technique have been proposed to obtain desired properties of the microspheres, loaded with the water soluble active principles.…”

Multivariate modeling of encapsulation and release of an ionizable drug from polymer microspheres

“…2). Low span values indicate narrow size distribution, reflecting the formation of a stable emulsion 32. The change in MS characteristics may be attributed to both the effect of pH on VRP ionization and the osmotic effect of buffer salts.…”