Micronization and microencapsulation of felodipine by supercritical carbon dioxide

Felodipine (FLD) is a poorly water-soluble drug. To improve its dissolution rate, the rapid expansion of supercritical solutions (RESS) technique was used to prepare micronized FLD drug particles, which were encapsulated in poly-(ethylene glycol) 4000 (PEG 4000). The physical properties of the encapsulated drug particles were characterized by a variety of analytical methods, including optical light microscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and powder X-ray diffraction (powder-XRD) and the dissolution behaviour of FLD was studied in the microparticles. The supercritical condition of micronized FLD occurred at a relatively high pressure and moderate temperature. FLD–PEG 4000 microparticles compared well with micronized FLD. RESS was effective in reducing the particle size of FLD; spot-shaped micronized FLD and popcorn-shaped FLD–PEG 4000 microparticles were observed. The particulate properties of the microparticles included a narrow distribution and uniform size. Thermodynamic analysis showed an implantation interaction between FLD and PEG 4000 molecules, but no polymorphism in the micronized FLD or FLD–PEG 4000 microparticles. FLD–PEG 4000 microparticles had a significantly faster drug dissolution rate than micronized FLD. These data show that RESS can be used to prepare FLD–PEG 4000 microparticles with small particle size (2–6 µm) and enhanced dissolution rate.