PubMed · 11639061
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G Fochi. 1999. [Not Available].. https://pubmed.ncbi.nlm.nih.gov/11639061/
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This study was performed to elucidate the influences of process and formulation design on the granulation process using power consumption and tensile strength measurements. In order to record and analyze the power consumption profile "in process" a computer program was developed to be used for optimal end-point control in reproducible granule production. The program analyzes and calculates a characteristical point, the turning point of the S-shaped ascent of the profile. The tensile strength expresses the cohesiveness between the powder particles, which is dependent on saturation and capillary pressure. In order to investigate the influence of the amount of liquid present in the granular material on tensile strength a device was developed. The maxima of tensile strength occurred at 90% saturation, whereas the maxima of power consumption were determined at 100% saturation. The measured tensile strength sigma (N/m(2)) equals to the volume specific cohesion (J/m(3)). The present work proved that the power consumption measurement is an alternative, simple and inexpensive method to determine the cohesion of powder particles. The turning point is introduced as a signature of the starting material and furthermore as a parameter for the cohesiveness of the starting material and therefore for optimal end-point detection at an early stage.
The rheological properties of the parenteral oil-in-water emulsion Intralipid were investigated. The viscosity data at different phase volumes correlated well with that obtained via a theoretical model developed by Yaron and Gal-Or. The model also describes the temperature dependence well. The effects of electrolyte addition were also investigated. Monovalent sodium chloride had practically no influence on viscosity. Calcium chloride, on the other hand, had a large impact on viscosity even at low concentrations. It was shown that the obtained maximum in viscosity coincided with the zeta-potential being close to zero. The resulting increase in viscosity is due to flocculation that leads to an increase in apparent phase volume. A similar behaviour was obtained with magnesium chloride with the difference that the maximum in viscosity was shifted to higher electrolyte concentrations. This is interpreted as that because magnesium binds strongly to the hydration water than does calcium. The addition of the negatively charged anti-coagulant heparin causes flocculation in the presence of small amounts of calcium. The amounts of calcium needed for such bridging flocculation is lower than what is needed in order to create a positive potential at the surfaces of the droplets. A fraction of the flocs is not broken down even by extensive shear.
In this study, the microspheres containing verapamil hydrochloride (VRP) were prepared with Eudragit RS 100 by solvent evaporation method. In the solvent evaporation method one of the parameters which affect to the formation and properties of the microspheres is the variations of drug/polymer ratios. The aim of our study is to examine the effects of this parameter on the VRP loaded microspheres. To achieve this purpose, only drug/polymer ratio was altered while the other formulation parameters were kept constant and percentage yield value, incorporation efficiency, particle size and distribution of the microspheres were analyzed and micrographs of the microspheres were taken to determine the effects of the increase in the polymer amount of formulations. All the dispersed phase viscosities were evaluated by comparing them with the variations in particle size and distribution of the microspheres. In vitro dissolution tests were done by using dissolution media with three different pH in sequence as half-change method with flow through cell and the effect of the variation in polymer ratio on drug dissolution was evaluated according to dissolution test results. As a result of our study, it is thought that the variation in drug/polymer ratios might have an influence on the physical characteristics of the microspheres and the increasing amount of polymer might be result in decreased drug dissolve.