1. Characterization of Lipid Based spherulites
The lipid spherulitic phase identified was the preferred state for proprietary formulation for
suspending insoluble drugs. An assay was performed to complement this formulation studies to
determine forwhich formulationsthe spherulitic phase is present and if lipid phase analysis can be
used to determine drug suspension behaviour. Also, samples were investigated for the effect of
additional ingredients on the formulations ability to suspend pharmaceuticals. The formulations
were quick, simple and safe to manufacture.
Abstract –
Structuredsurfactantsare lipidbasedspheruliticsystems that are formed by low- shearing which is
formulatedforsuspendingdrug.Thisstudyinvolvesthe characterizationof spherulitestodetermine
theirstructure,shape,size,numberandalsothe yieldpointtosuspendin-soluble drugbythe means
of optical microscopy,dynamiclight scattering and rheological studies. The lipid based spherulites
were identified as onion ring structures under bright field microscopy and these crystals visible
structuresundercrosspolarisationmicroscopy which displays a birefringent property. The number
of spherulites per millilitre of the suspension was also counted by haemocytometer. The size of
these spheruliteswasdeterminedusingagraticule andwere approximately 1-2 microns in size. The
sizesof these structures were compared with the results obtained by the dynamic light scattering;
where the size rangedfrom1-2 microns.Subsequently,rheologicalparametersuchasgeometry was
chosenbasedonthe size of the spherulites.The suspensionwasdilutedinordertomake it pourable
withhighyieldpointandshearthinningproperties.The geometry used was cone and plate and was
compared with concentric cylinders. It was found that 16% w/w is required in order to make the
suspension pourable and this dilution was selected to suspend acetaminophen. Rheology for the
suspension with the drug was performed that resulted in high yield point at 1/s shear rate. The
stability of these suspensions was analysed by centrifuging the sample at varying speeds.