56. Thote Amol J; Gupta Ram B Formation of nanoparticles of a hydrophilic drug using supercritical carbon dioxide and microencapsulation for sustained release. Disease-a-month : DM (2005), 51(6), 362-73.
The authors' purpose was to produce nanoparticles of a hydrophilic drug with use of supercrit. carbon dioxide (CO2), encapsulate the obtained nanoparticles into polymer microparticles with use of an anhyd. method and study their sustained in vitro drug release. The hydrophilic drug, dexamethasone phosphate, is dissolved in methanol and injected in supercrit. CO2 with an ultrasonic field for enhanced mol. mixing (supercrit. antisolvent technique with enhanced mass transfer [SAS-EM]). Supercrit. CO2 rapidly exts. methanol leading to instantaneous pptn. of drug nanoparticles. The nanoparticles are then encapsulated in poly(lactide-co-glycolide) (PLGA) polymer by use of the anhyd. solid-oil-oil technique. This results in a well-dispersed encapsulation of drug nanoparticles in polymer microspheres. In vitro drug release from these microparticles is studied. With supercrit. CO2 used as an antisolvent, nanoparticles of dexamethasone phosphate were obtained in the range of 150 to 200 nm. On encapsulation in polylactide coglycolide, composite microspheres of .apprx.70 mm were obtained. The in vitro drug release of these nanoparticles/microparticles composites shows sustained release of dexamethasone phosphate over a period of 700 h with almost no initial burst release. Nanoparticles of dexamethasone phosphate can be produced with the SAS-EM technique. When microencapsulated, these particles can provide sustained drug release without initial burst release. Because the complete process is anhyd., it can be easily extended to produce sustained release formulations of other hydrophilic drugs.