ABSTRACT
In solids manufacturing, many products require coating to provide the desired properties
(1). Contemporary fluidized bed equipment is widely used to coat substrates in a broad
range of particle sizes, from below 100mm up to and including tablets. The fluidized bed is available in various configurations, depending on the vendor, but principally, they are
based either on a conventional top spray, bottom spray (usually a variation of the Wurster
though other types of bottom spray are available), or tangential spray, referred to as a
rotor or centrifugal processor. A few iterations of the fluidized bed have been configured
for tablet coating, particularly for modified release products or the application of a potent
outer layer. This is primarily due to the very random and rapid mixing capability of air
suspension systems and the absence for consideration of the spatial orientation of the
tablets as they enter and exit the so-called “coating zone.” The mechanical stress to
which tablets are exposed is comparatively high and tablets and their coatings should be
formulated specifically for their intended use in the fluidized bed. Although air sus-
pension systems have enjoyed renewed interest for coating or layering of tablets, the
perforated pan remains the preferred method for most tablet coating applications.
