Page 133 - 69_01

VOL. 69 (1), MICROCÁPSULAS ORALES DE LIBERACIÓN CONTROLADA DE NAPROXENO

Microscopy studies and particle size distribution
Optical microscopy was used to evaluate the drug incorporation
and the surface shape of the microcapsules. Particle size was determined
by optical microscopy. Samples of microcapsules (200) were dispersed on
a slide and its diameter was evaluated. The microcapsules particle size
distribution was also evaluated by sieving.

Differential scanning calorimetry
Differential thermal analysis (heating cycles of 25ºC-280ºC) of
pure naproxen, empty Eudragit and empty Eudragit/Cutina microcapsules,
Eudragit and Eudragit/Cutina microcapsules containing naproxen,
mechanical mixtures of naproxen, Eudragit, Cutina and magnesium
stearate was carried out with a computer-interfaced Shimadzu differential
scanning calorimeter, Model DSC-50. The samples (2.6-2.8 mg), which
were stored in a desicator prior to the analysis, were sealed in aluminum
pans. The scanning rate throughout the investigation was 10ºC/min. All
tests were run in triplicate and the DSC cells were purged with nitrogen at
20.0 ml/min.

Release studies
The dissolution test was carried out using the European Pharma-
copoeia apparatus at a basket speed of 100 rpm. The dissolution medium
was 500 ml of a pH 7.4 phosphate buffer solution, maintained at 37ºC r
0.5ºC. At appropriate time intervals (30, 60, 120, 240, 360, 480 and 480
min), 25 ml of each was withdrawn and equal volume of medium was
added to maintain a constant volume. Samples were filtered, diluted and
analysed by UV spectophotometry at 331 nm on a Hitachi 2000 spectro-
photometer.

139