iii. Depth of granulation on the trays

iv. Surface temperature of oven, etc.

Because each product has specified airflow and air temperature for the drying

process. If the granulation bed has high depth or high density then the drying will

be inefficient. So, at scale-up stage fluidised bed dryer is the best alternative for

circulating hot air oven (Table 2.4).

6. Particle size reduction: Particle size distribution affects many compression factors

like flowability, tablet weight uniformity, content uniformity, the hardness of tablet,

the color of the tablet, compressibility and hence ultimately the quality of tablet.

The particle size distribution of granulation is determined by using multiple stacked

sieves of decreasing mesh openings. The particle size reduction of dried granulation

can be done by using screening device, oscillating granulator, hammer mill, sieving

device, etc.

Table 2.4: Scale-up considerations during drying

Name of equipment Scale-up consideration

Hot air oven Airflow

Air temperature

Surface temperature

Fluidised bed dryer Air flow rate

Inlet air temperature

Optimum load

The humidity of air entering

Tray dryer Airflow

Air temperature

Depth of granulation on trays

Monitoring of drying by use of moisture and temperature probes

Monitoring of drying times at specific temperature and specific air

flow rates for a particular product

Table 2.3: Scale-up considerations during addition of binders

Problems can be faced during scale-up Solutions to the respective problem

Binding agents may impart viscosity to the This can be avoided by adding all binding agents

granulating solution which makes transfer in the dry powder prior to granulation.

of fluid difficult.

General Considerations and Pilot-Plant Considerations for Different Dosage Forms 17

At laboratory-scale, the lubricants and glidants are usually added to the final

blend but at scale-up, they are added during sizing operation. This is done to avoid

agglomeration of some additives like magnesium stearate if added to the final blend

in large quantities in the blender (Table 2.5).

7. Compression: The ultimate critical step in the tablet formulation is compressing.

The success of tablet formulation depends on whether it can be compressed on a

high-speed tablet press. The tablet press performs the following functions during

compression (Table 2.6).

i. Filling of empty die

ii. Precompression (optional)