In the
tablet-pressing process, it is important that all ingredients be dry, powdered, and of uniform grain size as much as possible. The main guideline in manufacture is to ensure that the appropriate amount of active ingredient is equal in each tablet so ingredients should be well-mixed. Compressed tablets are exerted to great pressure in order to compact the material. If a sufficiently homogenous mix of the components cannot be obtained with simple mixing, the ingredients must be granulated prior to compression to assure an even distribution of the active compound in the final
tablet. Two basic techniques are used to prepare powders for granulation into a tablet: wet granulation and dry granulation.
Powders that can be mixed well do not require granulation and can be compressed into tablets through Direct Compression
Direct Compression
This method is used when a group of ingredients can be blended and placed in a tablet press to make a tablet without any of the ingredients having to be changed. This is not very common because many tablets have active pharamaceutical ingredients which will not allow for direct compression due to their concentration or the excipients used in formulation are not conducive to direct compression.
Granulation is the process of collecting particles together by creating bonds between them. There are several different methods of granulation. The most popular, which is used by over 70% of formulation in tablet manufacture is wet granulation. Dry granulation is another method used to form granules.
Wet granulation for tablets
Wet granulation is a process of using a liquid binder or adhesive to the power mixture. The amount of liquid can be properly managed, and overwetting will cause the granules to be too hard and underwetting will cause the granules to be too soft and friable. Aqueous solutions have the advantage of being safer to deal with than solvents.
Procedure of Wet Granulation for tablets
Step 1: Weighing and Blending - the active ingredient, filler, disintegration agents, are weighed and mixed.
Step 2: The wet granulate is prepared by adding the liquid binder/adhesive. Examples of binders/adhesives include aqueous preparations of cornstarch, natural gums such as acacia, cellulose derivatives such as methyl cellulose, CMC, gelatins, and povidone. Ingredients are placed within a granulator which helps ensure correct density of the composition.
Step 3: Screening the damp mass into pellets or granules
Step 4: Drying the granulation
Step 5: Dry screening: After the granules are dried, pass through a screen of smaller size than the one used for the wet mass to select granules of uniform size to allow even fill in the die cavity
Step 6: Lubrication- A dry lubricant, antiadherent and glidant are added to the granules either by dusting over the spread-out granules or by blending with the granules. Its reduces friction between the tablet and the walls of the die cavity. Antiadherent reduces sticking of the tablet to the die and punch.
Step 7:
Tableting: Last step in which the tablet is fed into the die cavity and then compressed between a lower and an upper punch.
Water may be used as the liquid binder, but sometimes many actives are not compatible with water. Water mixed into the powder can form bonds between powder particles that are strong enough to lock them in together. However, once the water dries, the powders may fall apart and therefore might not be strong enough to create and hold a bond. Povidone also known as polyvinyl pyrrolidone (PVP) is one of the most commonly used pharmaceutical binders. PVP and a solvent are mixed with the powders to form a bond during the process, and the solvent evaporates. Once the solvent evaporates and powders have formed a densely held mass, then the granulation is milled which results in formation of granules
Dry granulation for tablets
Wet granulation is a process of using a liquid binder or adhesive to the power mixture. The amount of liquid can be properly managed, and overwetting will cause the granules to be too hard and underwetting will cause the granules to be too soft and friable. Aqueous solutions have the advantage of being safer to deal with than solvents.
pharmaceutical validation
Procedure of Wet Granulation for tablets
Step 1: Weighing and Blending - the active ingredient, filler, disintegration agents, are weighed and mixed.
Step 2: The wet granulate is prepared by adding the liquid binder/adhesive. Examples of binders/adhesives include aqueous preparations of cornstarch, natural gums such as acacia, cellulose derivatives such as methyl cellulose, CMC, gelatins, and povidone. Ingredients are placed within a granulator which helps ensure correct density of the composition.
Step 3: Screening the damp mass into pellets or granules
Step 4: Drying the granulation
Step 5: Dry screening: After the granules are dried, pass through a screen of smaller size than the one used for the wet mass to select granules of uniform size to allow even fill in the die cavity
Step 6: Lubrication- A dry lubricant, antiadherent and glidant are added to the granules either by dusting over the spread-out granules or by blending with the granules. Its reduces friction between the tablet and the walls of the die cavity. Antiadherent reduces sticking of the tablet to the die and punch.
Step 7: Tableting: Last step in which the tablet is fed into the die cavity and then compressed between a lower and an upper punch.
Water may be used as the liquid binder, but sometimes many actives are not compatible with water. Water mixed into the powder can form bonds between powder particles that are strong enough to lock them in together. However, once the water dries, the powders may fall apart and therefore might not be strong enough to create and hold a bond. Povidone also known as polyvinyl pyrrolidone (PVP) is one of the most commonly used pharmaceutical binders. PVP and a solvent are mixed with the powders to form a bond during the process, and the solvent evaporates. Once the solvent evaporates and powders have formed a densely held mass, then the granulation is milled which results in formation of granules
Dry granulation for tablets
This process is used when the product needed to be granulated may be sensitive to moisture and heat. Dry granulation can be conducted on a press using slugging tooling or on a roller compactor commonly referred to as a chilsonator. Dry granulation equipment offers a wide range of pressure and roll types to attain proper densification. However the process may require repeated compaction steps to attain the proper granule end point.
Process times are often reduced and equipment requirements are streamlined; therefore the cost is reduced. However, dry granulation often produces a higher percentage of fines or noncompacted products, which could compromise the quality or create yield problems for the tablet. It requires drugs or excipients with cohesive properties.
Some granular chemicals are suitable for direct compression (free flowing) e.g. potassium chloride.
Tableting excipients with good flow characteristics and compressibility allow for direct compression of a variety of drugs.
Fluidized bed granulation
It is a multiple step process performed in the same vessel to pre-heat, granulate and dry the powders. It is today a commonly used method in pharmaceuticals because it allows the individual company to more fully control the powder preparation process. It requires only one piece of machinery that mixes all the powders and granules on a bed of air.
Tablet Compaction SimulatorTablet formulations are designed and tested using a laboratory machine called a Tablet Compaction Simulator or Powder Compaction Simulator. This is a computer controlled device that can measure the punch positions, punch pressures, friction forces, die wall pressures, and sometimes the tablet internal temperature during the compaction event. Numerous experiments with small quantities of different mixtures can be performed to optimise a formulation. Mathematically corrected punch motions can be programmed to simulate any type and model of production tablet press. Small differences in production machine stiffness can change the strain rate during compaction by large amounts, affecting temperature and compaction behaviour. To simulate true production conditions in today's high speed tablet presses, modern Compaction Simulators are very powerful and strong.
Initial quantities of active pharmaceutical ingredients are very expensive to produce, and using a Compaction Simulator reduces the amount of powder required for development.
Load controlled tests are particularly useful for designing multi-layer tablets where layer interface conditions must be studied.
Pharmaceutical Process Validation
Test data recorded by the Simulators must meet the regulations for security, completeness and quality to support new or modified drug filings, and show that the designed manufacturing process is robust and reliable.this website
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tablets dosage form advantages and disadvantages
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