Biomedical subjects

P Kleinebudde

Publications and source records attributed to P Kleinebudde.

22 records · Page 2Linked to original sources

PubMed1995

Use of a power-consumption-controlled extruder in the development of pellet formulations.

Shape is an important characteristic of pellets that is highly influenced by the water content of the extrudate during spheronization. The power-consumption-controlled extruder (pcc-extruder) is an appropriate tool to adjust the required water content to yield round pellets. For this purpose, it is necessary to run the extruder at a specific level of power consumption. In the first part of the study, this approach was employed to screen different drugs as well as excipients to prove the concept of the pcc-extruder. Usually round pellets were obtained but a few formulations did not produce round pellets. In the second part of the study, the influence of screw speed and powder feed rate on the required level of power consumption was investigated. A correlation between the water content and the shape of pellets was evident. To account for screw speed, it was necessary to adjust net power consumption instead of total power consumption. The influence of the screw speed on water content of extrudate and consequently on the shape of pellets was not significant in the studied range. Variations of the powder feed rate affected both the water content and the shape of pellets. However, the water content was not only dependent on the level of net power consumption. The specific power is the ratio of net power consumption to extrusion rate, and it correlates well with water content and pellet shape. Using the specific power, it is possible to adjust the net power consumption in response to changes in powder feed rate.

Acetaminophen↗

PubMed1995

Structure of disintegrating pellets with regard to fractal geometry.

PURPOSE: The aim of this study was to investigate the influence of the granulation liquid on pellet properties. METHODS: Pellets containing propyphenazone were obtained by extrusion/spheronization using different 2-propanol/water mixtures as granulation liquids. The pore structure of the pellets was determined by mercury porosimetry. The fractal dimension of the pore system was calculated according to the model of the Menger sponge. Further characterization included SEM-photographs, disintegration, dissolution and tensile strength. RESULTS: Fractions exceeding 40% 2-propanol in the fluid resulted in rapid dissolution rates of the pellets. This effect was caused by the rapid and complete disintegration of the pellets as compared to those obtained with less 2-propanol in the mixture. These phenomena were interpreted as being due to a change in the particle bonding of the pellets at concentrations of 40% 2-propanol. Evidence for this hypothesis resulted from the spheronization process, the tensile strength measurements and from SEM-photographs. The analysis of the pore system in terms of fractal dimensions implied a dependency of the fraction of 2-propanol in the granulation liquid on the pore structure. High fractions of 2-propanol resulted in lower fractal dimensions close to the dimension of the Menger sponge (2.727). CONCLUSIONS: The structure of pellets can be markedly influenced by the composition of the granulation liquid. Investigations of the pore system in terms of fractal geometry are more useful for the explanation of pharmaceutical properties than if the pure values for the porosity are taken.

1-Propanol↗

PubMed1994

Use of powdered cellulose for the production of pellets by extrusion/spheronization.

The use of powdered cellulose instead of microcrystalline cellulose in the extrusion/spheronization process was investigated. The aim of the study was to assess differences between two types of powdered cellulose using a 2(4-1) fractional factorial design. Water content and amount of binder were found to be most important while type of cellulose and screw speed had only negligible influence on the extrusion process and the resulting pellets. Pellets obtained with powdered celluloses showed higher porosities and faster dissolution rates compared with those made with microcrystalline cellulose. Image analysis was found to be an appropriate method for the simultaneous characterization of pellet size and shape.

Cellulose↗

PubMed1994

The power-consumption-controlled extruder: a tool for pellet production.

Based on the assumption that there is a link between power consumption of an extruder and pellet properties, a control circuit for power consumption was developed. Powder and granulation liquid are fed separately into a twin-screw extruder. The power consumption is controlled by varying the pump rate at a given powder-feed rate; consequently each level of power consumption results in a specific water content of the extrudate for a particular formulation. The shape of pellets depends almost entirely on the level of power consumption irrespective of formulation. The size of dry pellets is additionally affected by a shrinking factor which depends on the water content. The power-consumption-controlled extruder is an appropriate tool for the production of pellets. The system is able to adapt the water content for a formulation automatically.

Cellulose↗