PubMed · 8098744
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J C Berridge. 1993. Pharmaceutical analysis in a multidisciplinary development environment.. https://pubmed.ncbi.nlm.nih.gov/8098744/
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The effects of process conditions on the granulometric characteristics of a placebo formulation prepared in a 10 l high shear mixer by single-step melt granulation were studied. The factors under investigation were: binder grade, mixer load, presence of the deflector (all of analysed at two levels), binder concentration, impeller speed, massing time, type of impeller blades (these four at three levels) and jacket temperature (considered at four levels). Two granule characteristics were analysed: the geometric mean diameter and the percentage of particles finer than 315 microm. In order to screen simultaneously the above-mentioned factor levels, an asymmetrical factorial design was adopted, which allowed the reduction in the number of runs from 2592 to 25. Additionally, this technique permitted the selection of the factor levels which have the major 'weight' on the two granule characteristics under study. Two additional trials were performed to attest the screening validity.
A series of modified phospholipids (m-PC) possessing different acyl chains in position 2, from butanoyl to hexadecanoyl, were prepared by partial synthesis from soybean lysolecithin. They were used with soybean lecithin to construct phase diagrams containing ethanol as cosolvent, water and medium chain triglycerides (MCT) or isopropyl myristate (IPM) as oils. The weight ratios lecithin:m-PC and surfactants:ethanol were kept constant at 1:1. The results indicate that the m-PCs have a strong effect on the microemulsion (L) and liquid crystalline (LC) domains in the water-rich/oil-poor part of the phase diagrams, although all diagrams correspond to a single lecithin:m-PC ratio. On decreasing the acyl chain length, and thus increasing the hydrophilicity of the surfactant, there was a corresponding increase in the L area, which moved towards the aqueous corner of the phase diagrams. The LC phase was detected only in the presence of the hexadecanoyl derivative for the systems containing MCT, and it was not detected only in the presence of the butanoyl derivative for the systems containing IPM. The use of a second hydrophilic surfactant to adjust the packing properties of the lecithin-alcohol systems, and/or to increase the fluidity of the surfactant film, increased the region of existence of the isotropic systems. This may be of importance in the formulation of drug delivery systems, especially those which are diluted by biological fluids upon administration.
Magnetic resonance imaging (MRI) has been applied to the evaluation of the distribution of water in extrudates produced by extruding pastes. Two model drugs similar in chemical structure were mixed with microcrystalline cellulose (MCC) and with two different amounts of water and extruded at two different extrusion speeds using a ram extruder. Extrudates were collected during the steady-state stage of the extrusion profile and were analysed for the water distribution using MRI. The percolation threshold for each sample was calculated to evaluate the degree of water structure within the sample. The water distribution inside the extrudates was surprisingly uniform. The extrudates produced using the faster extrusion speed had a significant lower percolation threshold, which suggests the existence of a greater water structure in the extrudates. A significant correlation was found between the percolation threshold and the extrusion force, which had been used to provide the extrudates.