Poly(epsilon-caprolactone) microparticles formed by the emulsion-evaporation method: effect of the variables of the different steps of the process on their size.

In the present work the influence of the variables of the microencapsulation procedure on the size of poly (epsilon-caprolactone) microparticles (PECL-MP) obtained by the solvent evaporation method is analysed. This study will allow to choose the work conditions necessary to obtain a suitable PECL-MP size for parenteral administration. Agitation rate in the emulsion formation step, polymer concentration and organic/aqueous phase volume ratio were the variables of the microencapsulation procedure that showed a highest influence on the PECL-MP size. High polymer concentrations and low internal phase volumes had a negative effect on the microencapsulation yield. Neither the conditions of the organic solvent evaporation nor the freeze-dry process (when a cryoprotector as threalose was used) influenced on PECL-MP size. The usefulness of this study was confirmed by getting PECL-MP loaded with naloxone and with a mean diameter within 30-40 microm, suitable for parenteral administration.