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Abstract
The production and physicochemical characterisation of spray chilled Gelucire 50/13
microspheres is described with a view to improving the dissolution of a poorly water-soluble
drug, piroxicam, and understanding the fundamental mechanisms associated with the
improved drug release. Thermorheological testing was developed as a fast screening
method for predicting the processability of dispersions for spray chilling preparation.
Spray chilled piroxicam loaded microspheres were spherical in shape with a median
diameter of circa 150 microm. DSC indicated no interaction between piroxicam and lipid
matrix, while HSM studies performed in polarized light mode indicated that the spheres
contained distinct drug crystals. Polarising light microscopy and small-angle XRD
investigations on the hydration behaviour of the lipid and the spray chilled microspheres
revealed the formation of liquid crystalline phases depending on the degree of hydration.
The dissolution behaviour of the piroxicam loaded microspheres showed significant
improvements compared to drug alone. The particle size, drug loading and aging of
the microspheres were all found to have an influence on the release behaviour. It
was proposed that Gelucire 50/13 microspheres release the entrapped piroxicam via
formation of a lyotropic liquid crystalline phase, which allows dissolution of the
drug particles in a finely divided, high surface area and well-wetted state.