The Effect of Design and Size of the Fluid-Bed Equipment on the Particle Size-Dependent Trend of Particle Coating Thickness and Drug Prolonged-Release Profile.

The focus of the current work is to study and demonstrate the impact of the design, the scale, and settings of fluid-bed coating equipment on the differences in pellet coating thickness, which in case of prolonged-release pellets dictates the drug release. In the first set of coating experiments, the pellet cores were coated with the Tartrazine dye with the aim of estimating the coating equipment performance in terms of coating thickness distribution, assessed through color hue. In the second set, drug-layered pellets were film-coated with prolonged-release coating and dissolution profile tests were performed to estimate the thickness and uniformity of the coating thickness among differently sized pellets. In both study parts, film coating was performed at the laboratory and the pilot scale and essentially two types of distribution plate and different height adjustments of the draft tube were compared. The dye coating study proved to be extremely useful, as the results enable process correction and the optimal use of the process equipment in combination with the appropriate process parameters. Preferential film coating of larger drug-containing pellets was confirmed on the laboratory scale, while on the pilot scale, it was possible to achieve preferential coating of smaller pellets using rational alternatives of settings, which is desirable in terms of particle size-independent drug release profile of such prolonged-release dosage forms.

Fluid-bed coater modifications and study of their influence on the coating process of pellets.

OBJECTIVE: In this study, different modifications of bottom spray fluid-bed coater with draft tube inserted were characterized and evaluated. MATERIALS AND METHODS: After coating the neutral pellets with polymeric solution comprising coloring agent pellet batches were characterized for coating variation, yield and degree of agglomeration. RESULTS: Funnel-shaped distribution plate was found to improve process yield and decrease the degree of agglomeration at selected values of process parameters, whereas coating uniformity was worse in all cases when compared to conventional Wurster chamber. Results of the coating chamber with the swirl airflow generator indicate more uniform deposition of the coating material and in some cases an improved process yield and decreased formation of agglomerates when compared to conventional Wurster chamber. In series of experiments using Wurster chamber, having tangentially oriented air intake slots, which enabled introduction of air above the distribution plate, coating layer was more uniformly deposited on the pellet cores and formation of agglomerates was lower compared to the results obtained in a conventional Wurster coating chamber. CONCLUSION: Modifications of Wurster coating process by introducing swirling air motion within the draft tube or by introduction of air above the distribution plate have at selected values of process parameters resulted in reduced per-particle coating variation, degree of agglomeration and improved process yield.