Coating Process Optimization

Tablet coating usually takes place within a perforated rotating drum. There are angled baffles placed in the drum that, along with the air flow inside, help mix the tablet bed. This allows the tablets to be lifted and turned from the peripheries to the centres of the drum to ensure that all surfaces of the tablets are evenly and uniformly coated with the sprayed coating or deposited coating. The atmosphere within this rotating drum needs to be closely controlled for temperature and dew point or relative humidity to ensure that the coating is uniform and smooth in appearance.

Once the coating is applied the drying of the coating takes place by drawing heated air through the tablet bed from a fan. This air flow also requires temperature, humidity and volume control to ensure controlled drying and extraction. Monitoring the dew point of both the inflow and outflow of this air gives an indication of the progress of the drying process. This allows the drying time to be kept to a minimum, reducing overall costs of the drying process.

Knowledge of the water activity of pharmaceutical solids (proteins, drugs, and excipients) is essential to obtain a solid dosage form with optimal chemical, physical, microbial, and shelf-life properties. Water activity (aw) influences the chemical stability, microbial stability, flow properties, compaction, hardness, and dissolution rate of dosage forms of pharmaceuticals, proteins, biopharmaceuticals, nutraceuticals, and phytochemicals.