The miniwid-coater: I. design and evaluation of a temperature-controlled miniature fluid-bed pan coater

A novel miniature laboratory-scale pan coater has been developed. Small batches of 50 to 100 g of pellets, granules, large crystalls and small tablets allow the formulation development with minimal quantities of valuable drugs and new active ingredients. Although originally it is a pan coater, the core bed will be slightly fluidized by the inlet air flow due to the small dimensions of the coating pan. This allows a rapid drying and the loss of coating materials will be negligible.

A computer was used to control the core bed temperature during the coating process by varying the spraying rate of an analytical dosing pump. Additionally, the drying air temperature can be adopted. It was possible to change the parameters during the process to optimize the operation conditions within one run. The computer program described in this article provides a constant bed temperature with a precision of ± 0.3 °C.

In the MiniWiD-Coater, neutral pellets have been loaded with bisacodyl and then enteric-coated with aqueous dispersions of Eudragit L 30 D. Batch homogeneity and reproducibility were excellent. Friability of the cores and abrasion of the coat remained low. The loss of coating material during operation was always below 5 %.