Page 136 - 69_01

D. FERREIRA Y COLS. ANAL. REAL ACAD. NAL. FARM

empty microcapsules. However, in the case of the melting phase transi-
tion of pure naproxen, a sharp endotherm was observed at approximately
155ºC corresponding exactly to the melting point of naproxen. To shed
further light on the nature of Eudragit-naproxen interaction, different
mechanical mixtures were prepared and examined by DSC. When the
naproxen content in the mixtures was decreased, the peak at 155ºC
decreased and became negligible at approximately 50% naproxen. When
the microcapsules naproxen content was about 15%, the thermal behav-
iour of naproxen microcapsules was similar to the observed with pure
Eudragit, as the peak at 155ºC became negligible.

The microscopic analysis of microcapsules containing naproxen
revealed its spherical shape. As it can be observed in Figure 2, the
morphological examination of the microcapsules, performed at the
beginning and at different times of the release study by optical micros-
copy, showed that the products were homogeneous with corrugated
surfaces and pores. Higher magnification revealed surface shrinkage.
After dissolution test the microcapsules did not change in shape, which
suggests that naproxen diffused out through the minor pores and channels.

142