Granulation

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  • Created by: LBCW0502
  • Created on: 06-10-18 18:17
What is granulation?
The process in which primary powder particles are made to adhere (liquid bind/wet, compression/dry) to form larger, multiple particle entities called granules
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Why is granulation used?
Improves compressibility, improves flow properties, prevents segregation, improves appearance, improves mixing properties, avoids, dustiness, densifies material (granulation increases particle size)
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What are the two general granulation methods?
Wet granulation and dry granulation
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Describe the process of wet granulation
Blend powders (add binder). Moist mass (sieve). Moist agglomerates (dry). Dried granules (sieve). Sized granules - process involves heat and water
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Describe the process of dry granulation (slugging)
Blend powders (compression). Slug (mill). Granules (sieve). Sized granules - process required when producing tablets from highly moisture and heat sensitive compounds
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Describe features of blend and moisten
Solid components (drug and excipients). Liquid components (solvent and binder). Granulation fluid added to dry powder and dry takes place
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Describe features of sieving
After wet massing, the moist mass is pressed through a sieve or extruder to size granules
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What happens if the mass is too moist?
Strings will form
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What happens if the mass is too dry?
Granules will fall apart
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Describe features when mass is dried
Primary particles of granules are held together by solid bridges. These may be composed of either bridges of hardening binding agent or bridges of crystallised drug or excipient or a combination
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What are the important questions to consider about drying?
Does heat damage drug/excipients? Does drying cause changes in solid state? Is it air free from microbial contamination? How much energy is required to remove the liquid? How much powder can be dried at one time? Cost?
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What are the problems with drying?
Solute migration (concentration of drug on the surface of particles). Uneven distribution of drug upon compression (decrease dose uniformity), undesired interactions between drug/excipients, uneven colouring
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What are the limitations of wet granulation?
Cost (labor/time/equipment/energy, space). Loss of material (processing). Stability (moisture-sensitive, thermolabile drugs, polymorphism). Multiple processing steps (complexity/control difficult). Incompability (formulation components)
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What are the four types of pharmaceutical wet granulation equipment?
High speed shear mixer/granulators, fluidised granulators, extrusion spheronisers/pelletisers, spray driers
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Describe the process of high-speed shear mixer/granulators
Blending and wet massing is carried out using an impeller and a chopper. Mixing, densification and agglomeration are achieved through shear and compaction force exerted by impeller
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What are the advantages of high-speed shear mixer/granulators?
Short processing time, less liquid binder is required compared with fluidised-bed granulation, highly cohesive material can be granulated
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What are the disadvantages of high-speed shear mixer/granulators?
Moist mass would need to be transferred to a granulator (oscillating granulator). If excess liquid is added at wet massing stage, strings of material will be formed and if the mix is too dry, the mass will be sieved to a powder and granules will not
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Describe how fluidised-bed granulators work
Fluid bed granulation is a process by which granules are produced in a single step by spraying a binder solution onto a fluidised powder bed
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What are the advantages of fluidised-bed granulators?
Single step process, fine homogeneous particles, free flowing powders
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What are the disadvantages of fluidised-bed granulators?
Expensive, optimisation of process parameters affecting granulation needs extensive development work (initial formulation/scale-up to production). Long process. Numerous apparatus/process/parameters affect quality of granulation. Set up computer
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Describe how spray-driers work
A granulation technique that converts liquid into dry powders in a single step. This method removes moisture instantly
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What are the advantages of spray-driers?
Rapid process, ability to be operated continuously, suitable for heat sensitive products (able to adjust the heat)
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What are the disadvantages of spray-driers?
Bulky, expensive, overall thermal efficiency is low as air must be still hot enough when it leaves dryer to avoid condensation of moisture. Large volumes of heated air pass through chamber without contacting particles (not in drying process)
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Describe the process of extrusion and spheronisation
Multiple step process capable of making uniform spherical particles. It is primarily used a a method to produce particulates for controlled release application
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What are the advantages of extrusion and spheronisation?
Incorporates higher levels of API without producing larger particles. Applicable for both immediate and controlled release dosage forms
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What are the disadvantages of extrusion and spheronisation?
Labour-intensive process, should only be considered when other methods of granulation are either not satisfactory or inappropriate
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Describe how hot melt extrusion works
A size enlargement process in which a hot melt binder is used to bind primary powder particles into granules/pellets. (Feeding, compounding, downstreaming)
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What are the advantages of hot melt extrusion?
Aqueous wet granulation is avoided so damage to hydrolytic drug molecules is minimised. Avoids use of organic solvents.
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What are the disadvantages of hot melt extrusion
Thermal degradation. Immediate release products - little alternative to use of PEGs
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What are the advantages of dry granulation?
Ideal for moisture sensitive material. Ideal for heat sensitive material. Ideal for improved disintegration (no binder)
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What are the disadvantages of dry granulation?
Requires a specialised heavy duty tablet press to form slug. Poor colour distribution uniformity. Tends to create more dust, increasing the potential of contamination. High pressures and temperatures may cause polymorphisms
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Other cards in this set

Card 2

Front

Why is granulation used?

Back

Improves compressibility, improves flow properties, prevents segregation, improves appearance, improves mixing properties, avoids, dustiness, densifies material (granulation increases particle size)

Card 3

Front

What are the two general granulation methods?

Back

Preview of the front of card 3

Card 4

Front

Describe the process of wet granulation

Back

Preview of the front of card 4

Card 5

Front

Describe the process of dry granulation (slugging)

Back

Preview of the front of card 5
View more cards

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