The coating of pharmaceutical products in fluidized bed has gone through outstanding improvements since its creation in the 1950’s. This is so because at first organic solvents were used in the sheathing solutions. However, due to both environmental and health issues, they were prohibited and nowadays aqueous solutions are in use, which makes the drying process more difficult. Thus, the technology involved in the process required improving so that feasibility was maintained.
This coating is made by using a hot fluidized bed of dried particles and the injection or atomization of a salt solution. Growth takes place through successive spraying followed by particle drying.
Coating is made through several fluidized bed processes and types, which differ from each other mainly in the aspect of the solution atomizer location, occurring in different positions, either above, below or even by the side of the bed.
The tablets that undergo the coating process must be normally preheated (42°C to 46°C) in order to achieve a satisfactory sheathing. In addition, the bed must be operate in previous condition with the tablets and without the injection of solution so that dust and fragments between medicines can be removed. The average size and the size distribution of product can be controlled by adjusting the feeding rate of solid and liquid.
The main purpose of the coating in the case of medicines is to cover unpleasant flavors, release drug substance in the organism in a controlled mood or make medicine useful life longer.