Unit Operations during manufacture of Tablets:

Unit Operations:

The manufacture of Tablets is a complex multi-stage process under which the starting materials change their physical characteristics a number of times before the final dosage form is produced.

Numerous unit operations are involved in making Tablets including sifting, mixing, granulation, drying, sizing, blending, lubrication, compression and coating.

DISPENSING OF RAW MATERIALS (API & Excipients):

• Dispensing is the first step in any pharmaceutical manufacturing process.
• Dispensing is one of the most critical steps in pharmaceutical manufacturing; as during this step, the weight of each ingredient in the mixture is determined according to dose.
• Dispensing may be done manually by hand scooping from primary containers and weighing each ingredient on a weigh scale.

SIFTING OF DISPENSED RAW MATERIALS:

• All the dispensed raw materials will be subjected for security sifting by using sifters (Vibratory / mechanical sifters) and sieves to remove any extraneous contaminations from the materials.
• Sifting will also use to de-lump the materials (if any)
• Before and after the sifting operation, sieve integrity will be verified.

GRANULATION:

Granulation may be defined as a size enlargement process which converts small particles into physically stronger & larger agglomerates

Types of Granulations:

• Wet Granulation
• Dry Granulation
• Direct compression

Wet Granulation:

• In wet granulation, a liquid (binder solution) is required in the manufacture of granules
• Wet granulation is a popular technique within the pharmaceutical industry for the manufacture of Tablets
• Wet granulation process involves dry mixing of raw materials, preparation of binder solution, addition of binder solution, and wet mixing of materials to form granules.

Dry Granulation:

• Dry granulation process is used to form granules without using a liquid solution in case of moisture and heat sensitive products.
• Dry granulation process involves mixing of materials, compaction into slugs / flakes, and milling.

Direct compression:

• The term direct compression is defined as the process by which Tablets are compressed directly from powder mixture of API and suitable excipients.
• No pre-treatment of powder blend by wet or dry granulation is required.

DRYING:

• Drying is a most important step in the formulation and development of pharmaceutical product. It is important to keep the residual moisture low enough to prevent product deterioration and ensure free flowing properties.
• The commonly used dryer includes Fluidized – bed dryer, Vacuum tray dryer, Microwave dryer, Spray dryer, Freeze dryer, Turbo – tray dryer, Pan dryer, etc.

SIZING / MILLING:

• The sizing (size reduction, milling, crushing, grinding, pulverization) is an impotent step (unit operation) involved in the Tablet manufacturing.
• In manufacturing of compressed Tablet, the mixing or blending of several solid ingredients of pharmaceuticals is easier and more uniform if the ingredients are approximately of same size.
• This provides a greater uniformity of dose. A fine particle size is essential in case of lubricant mixing with granules for its proper function.

BLENDING AND LUBRICATION:

• The successful mixing of powder is acknowledged to be more difficult unit operation because, unlike the situation with liquid, perfect homogeneity is practically unattainable.
• Each process of mixing has optimum mixing time and so prolonged mixing may result in an undesired product. So, the optimum mixing time and mixing speed are to be evaluated.
• Blending is a critical unit operation in pharmaceutical manufacturing, as it is a prerequisite for the homogenous distribution of a drug’s components.
• Lubricants reduce the friction between the tablet and the die metal surface, which reduces the ejection force and helps to ensure that the tablet is cleanly ejected and without cracking or breakage.
• The various blenders used include octagonal blender, bin blender, double cone blender, etc

COMPRESSION:

• Reducing the bulk volume of a powder by applying mechanical force so as to form a defined shape of desired weight and strength is called Compression
• Tablet compression is the process of squeezing powders together and driving out the air between the particles, resulting in a compressed tablet.
• The compression is done either by single punch machine or by multi station machine.
• It can make the Tablet in many shapes, although they are usually round or oval, also it can press the name of the manufacturer or the product into the top of Tablet.

COATING:

• Coating can be defined as a physical deposition of a layer on tablet surface (enteric, film, sugar) for the purpose of masking the taste, odor, appearance, physical/ chemical protection or to control the drug release.
• The Tablets are placed within the coating machine and agitated
• The coating solution is sprayed on to the surface of Tablets
• Warm air is passed over the Tablets to facilitate removal of solvent from the absorbed layer of coating solution on the surface of Tablets
• When the solvent has evaporated, the Tablets will be coated with the solid component of the original coating solution.