Preparation and Characterization of Polyvinyl Acetate (Kollidon® SR) Microspheres Containing Diclofenac Sodium I: Effect of Stirring Rate and Total Solid Content

Abstract

Microspheres were prepared by W/O emulsification solvent evaporation technique where
Diclofenac Sodium (DS) and Kollidon® SR (KSR) were used as model drug and polymer respectively. Light
liquid paraffin (LLP) was used as oil phase and 1% (w/w of the continuum) of span 60 was used for
emulsification. Microspheres were prepared using different stirring rate (1500, 2000, 2500, 3000 rpm) and
different total solid content of the system (0.08%, 0.16%, 0.24% w/w of the continuum). Microsphere morphology
was examined with the help of Scanning Electron Microscope (SEM) and particle size distribution was analyzed
by Mastersizer 2000. Larger microspheres were obtained with decreasing stirring rate. Increase in solid content of
the system also increased microsphere size. Drug loading was also found to be affected due to these preparative
variables. In vitro dissolution study was performed in a USP XXX paddle apparatus (type 2). Dissolution media
was buffer of pH 7.2, paddle speed was 50 rpm and dissolution temperature was maintained at 37 ± 0.5°C. Release
of DS from KSR microspheres was found to follow higuchi mechanism. DS release was increased with increased
stirring rate. But increased solid content of the system resulted in reduced release of DS. Normalized release rate
of DS was also found to be affected by these preparative variables. Release rates were found increased with
increased stirring rate whereas rates were found decreased with increased solid content of the system.