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Umang offers road to Pelletisation through Spher'odization
Express Pharma Pulse June 29, 2000 |
Pellets are being increasingly used in the manufacture of sustained release drugs. The advantages of the sustained release drugs are well known. Some of them are:
- Extended daytime and nighttime activity of the drug.
- Potential for reduced incidence of side effects.
- Reduced dosage frequency.
- Increased patient compliance Patients who are required to take 1 or 2 tablets a day are thought to be less likely to forget a dose than if they are required to take 3 or 4 times a day.
- Potential lower daily cost to patient due to fewer dosage units used.
Pellets ensure improved flow properties, and flexibility in formulation development and manufacture. If the pellet surface is smooth it allows a thick coat of the drug on the pellet. The thickness of the coat determines the rate at which the drug is released from the coated particles.
The smooth surface and the uniform size of the pellets allows uniform coating not only for each pellet but also from batch to batch. By selecting the proper formulation, processing conditions and processing equipment it is possible to attain smooth surfaced and uniform pellets. The beads or granules of different thicknesses of coatings are blended in the desired proportions to give the desired effect. The coating material may be coloured with a dye material so that the beads of different coating thicknesses will be darker in colour and distinguishable from those having fewer coats.
Techniques to produce the pellets
The reproducibility of pellet size distribution, surface area, its smoothness and density of the pellet in addition to reproducibility of morphologic properties of the pellets, should become the criteria by which a process is selected.
The coating pan technique One of the oldest process for manufacturing spherical pellets is the agglomeration granulation in coating pans i.e., which involves layering process Layering involves the deposition of successive layers of an active compound on to the seeds. However the coating pan technique which is an outdated process currently had various disadvantages: It was a noise polluting process, there was considerable loss of drug. It was very much labour dependent and a very time consuming process.
Besides uniform coating of the pellets does not take place. Since this process is an outdated technology the discussion and comparison will be restricted to Extrusion Spher'oidization and fluid bed processing
Extrusion and Spher'oidization
The pelletisation process changed dramatically after the introduction of the extruder and spher'oidizer. This process typically involves first a day blending of ingredients in a mixer followed by a wet mixing with the binding solution to form a dough or paste. The wet mass is then extruded using the extruder. The material comes out in the form of extrudates (vermicilli like material) of equal length. The extrudates are then put on to the bed of the spher'oidizer. In the spher'oidizer, the extrudes are spun and rolled to break into shorter cylinders and then with the further rolling they are converted into spherical uniform beads.
Fluid bed processing
Fluid bed processing was used in the pharmaceutical industry for the past 30 years. 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 fluid 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, instantize 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 different operations just by changing the insert.
Extrusion-Spher'oidization v/s Fluid bed processing
A narrower particle size distribution can be obtained by using extrusion. spher'oidization technique.
Extruder-Spher'oidizer process is much more useful where larger capacity outputs are required.
Capital cost incurred is much lesser incase of extruder and spher'oidizer for production size machines.
Roto-processor as a single unit can be used to form and dry the spherical beads of the desired particle size, range and density. It can also be used for layering of the beads and also for coating the beads.
Further processing of dried granules such as application of sustained released coat can be accomplished without removal of the pellets from the roto-processor.
In some cases by selection of proper excipients and by controlling other variable parameters similar spherical granules can be produced using either of the techniques. For some formulations one of the process may be more appropriate than the other.
The choice of the appropriate equipment should be done only after appropriate trials using both the technique.
For further details contact:
Umang Pharmatech Pvt. Ltd.
D-13, Nav Monica, C.S.T. Road, Opp. University Campus, Kalina, Mumbai-400 098.
Tel.: 6126654, Fax: 0091-22-6174504 |
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