Dispensing (weighing and measuring)

 

Dispensing (weighing and measuring)

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 by purely manual by hand scooping from primary containers and weighing each ingredient by hand on a weigh scale, manual weighing with material lifting assistance like Vacuum transfer and Bag lifters, manual or assisted transfer with automated weighing on weigh table, manual or assisted filling of loss-in weight dispensing system, automated dispensaries with mechanical devices such as vacuum loading system and screw feed system. Issues like weighing accuracy, dust control laminar air flow booths, glove boxes), during manual handling, lost control of each ingredient, material movement into and out of dispensary should be considered during dispensing.

 

Sizing

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.

Advantages associated with size reduction in tablet manufacture are as follows:

• It increases surface area, which may enhance an active ingredient’s dissolution rate and hence bioavailability.
• Improved the tablet-to-tablet content uniformity by virtue of the increased number of particles per unit weight.
• Controlled particle size distribution of dry granulation or mix to promote better flow of mixture in tablet machine.
• Improved flow properties of raw materials.
• Improved colour and/or active ingredient dispersion in tablet excipients.
• Uniformly sized wet granulation to promote uniform drying.

There are also certain disadvantages associated with this unit operation if not controlled properly. They are as follows:

• A possible change in polymorphic form of the active ingredient, rendering it less or totally inactive, or unstable.
• A decrease in bulk density of active compound and/or excipients, which may cause flow problem and segregation in the mix.
• An increase in surface area from size reduction may promote the adsorption of air, which may inhibit wettability of the drug to the extent that it becomes the limiting factor in dissolution rate.

A number of different types of machine may be used for the dry sizing or milling process depending on whether gentle screening or particle milling is needed. The ranges of equipment employed for this process includes Fluid energy mill, Colloidal mill, Ball mill, Hammer mill, Cutting mill, Roller mill, Conical mill, etc.