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Handling and dosing of micronized powders
Powder at the centre of consideration
The behavior of powders is determined by numerous parameters, such as particle size distribution, particle shape, particle density, melting temperature, hygroscopicity and the tendency to electrostatic charging etc. This explains the very differing behavior of the various powders, for example during feeding and dosing, and requires knowledge as exact as possible about the material to be handled. Harro Höfliger therefore offers its customers as an introduction to a joint project a powder material analysis which is then invoked as the basis for selection of the most suitable dosing system. At the same time this analysis provides valuable indications as to which environmental conditions, such as temperature and relative humidity, have to be ensured during the later processing of the powder in the machine or in the production rooms. The adhesive behavior to different materials can also already be investigated at this stage. This has a decisive influence on the material selection for all parts that come into contact with the product.
Höfliger has made a name for itself on the „micronized powder“ method during the past 10 years by developing and implementing production methods and possible solutions for its customers, as regards manufacturing and packing pharmaceutical products.In this case, a predetermined dose of powder is applicated into the lungs (pulmonary) or over the nasal mucous membrane (nasal) and distributed in the blood stream.
At Höfliger, the competence necessary for handling pharmaceutical products is combined with highly technical expertise in the sectors for process, monitoring and control engineering.If one takes the example for processing different types of micronized powder, it is possible to demonstrate how the obstacles arising during the development of a new procedure can be successfully overcome. The ability to process micronized powder and the selection for a certain dosing procedure depends largely on the physical properties of the respective powder involved.
Not until a powder has been defined and classified can the selection of one or several suitable dosing systems be made. Once the selection has been made, further steps towards developing the optimum production process can be taken. Here it is decisive that the pharmacist has authoritative involvement in the development and also plays a role in deciding what steps should be taken next. These are, for instance, questions as to whether experiments with differing dosing procedures should be undertaken or whether experimental set-ups should possibly be designed and installed. Depending on the complexity of such a development project, a step-by-step process is of decisive advantage compared to a direct machine development. This process clearly focuses on dialogue and communication with the pharmacist.
The selected dosing systems should be tested with the agent-containing original formulations, if possible. While in theory it seems to be simple to produce constant conditions, hands-on tests will show that problems can occur quite frequently, such as:
- Tolerances in the powder production process
- Fluctuations of the ambient environmental conditions (temperature, relative humidity)
- Uneven distribution of the powder density
- Change of powder structure (grain size distribution, agglomeration, desagglomeration)
Starting with the production of the powder, critical parameters must be kept within very narrow tolerances, which, however, will not automatically exclude that for example the powder density may change during the downstream filling process. This is dependent, for instance, on the time between the production and filling and on the mechanical treatment of the powder during the filling procedure. Using constructive means, influence can thereby be brought to bear at an early stage.