|
Fluid Bed Systems: Will they suit your requirements?
Pharma Technology Trends March 1, 2001 |
All the operations like formation of beads, layering of the beads, agglomeration, enteric coating, tastemasking, drying are possible by the open system and fluid bed system. However, in fluid bed system all the operations can be carried out from a single machine by changing the insert - by R. Budhraja.
Fluid bed processing is being used in the pharmaceutical industry for the past three decades. The technology was originally developed specifically for rapid drying. Over the years, fluid bed processing has come into routine use for other applications such as particle coating, pellet coating, agglomerations, drug layering and pellet formation. The improvement in the technology is driven by the pharmaceutical industry and the manufacturers of the equipment.
A fluidized bed is a bed on which the particles or pellets are put, and a stream of air or gas passes upward through the particles at a rate great enough to set them in motion. As the air travels through the particle bed it imparts unique properties to the bed. It is possible to propagate a wave motion in the bed, which creates the potential for improved mixing. The intense mixing of the particles results in isothermal property.
Thus the fluid bed can be used to dry the wet product agglomerate particles, improve the flow properties, instantise the product or produce coated particles for controlled release or taste masking. As per the requirements of the pharmaceutical industry, the manufacturers of pharmaceutical machineries have developed the fluid bed processor wherein it is possible to perform the different operations just by changing the insert.
All the operations like formation of beads, layering of the beads, agglomeration, enteric coating, tastemasking, drying are possible in the open system and fluid bed system. The difference being that in case of the former all the operations can be carried out using different machines whereas in the latter all the operations are possible in one machine by changing the insert. The fluid bed system is more preferred in case the development of the product requires a complete pollution free environment and more automisation and sophisticated controls.
In case of the fluid bed system three inserts are possible. Each insert differs in terms of the spraying pattern. Using each insert different operations are possible.
Wurster Insert (bottom spray insert)
Principle of operation
The beads are kept in the product chamber and are coated with the solution with help of a Wurster design product chamber with bottom spray nozzle and partition in the middle.
The beads when coated with the solution are airborne to such a height that when they reach near the filter assembly they start falling back and are fairly dry when reaching back in the product chamber for further coating.
This process continues till the desired level of coating is achieved.
Operations possible
Particle coating (from 75 microns - 150 microns) Powder coating (from 10 micron and above) (optional) Pellet coating. Extrusion coating
Top spray insert
Principle of operation
Raw materials are mixed in a product container of the Fluid Bed Processor and granulation is achieved by spraying binder solutions in atomised form. Simultaneous drying can ensure achieving desired particle size and lubriction is done in the same container.
Operations possible
Top spray coating
Fluid bed drier.
Top spray granulation.
Rotoprocessor insert (tangential spray insert)
Principle of operation
The principle of operation is that tangential nozzles are fixed above the rotating plate so as to do different operation using the same insert. The rotating plate is a specially designed perforated plate so that the powder does not fall down and at the same time air can come through the plate creating fluidized effect in the processor.
The uniformity in this type of coating is best and the wastage is the minimum as the spray nozzle is embedded within the bed.
Operations possible
Tangential coating
Tangential granulation
Pallet formation
Pellet formation Pellet drug loading on dummy beads (N.P.S.)
Concave tablet coating.
Depending on the application either of the inserts could be used. However inorder to asses the applicability appropriate trials and guidance be take on using al the inserts.
- The author is managing director of Umang Pharmatech Pvt. Ltd. |
|
|
