Crospovidone can be successfully employed as a spheronization aid to produce good pellets without the need of a binder, unlike most of the previously proposed materials. This study exemplified the enormous potential of crospovidone to serve as a competent alternative to MCC in the production of pellets by extrusion-spheronization.

Spheronization is an agglomerative size enlargement process for producing spherical agglomerates that have many technological and therapeutical advantages. Rotary processing is an efficient multistage, single-pot spheroid production method. The rotary processor can be used for spheroid production, drying as well as coating. In the course of spheroid production, centrifugal, fluidizing, and gravitational forces act upon the product from different directions and collectively contribute to the spheroid formation process during rotary processing. The outcome of the process depends on the complex interactions between the equipment, formulation, and process variables.

Wet granulation technique is often employed in the preparation of free flowing agglomerates. It is essential that the agglomerates/granules produced were suitably dried prior to further processing such as tabletting, capsule or sachet filling. The drying process can have an impact on the final properties of granules and it has been reported that solute migration, overheating and structural damages of granules were not uncommon in conventional drying methods. 1,2) Often, the properties of the granules have been found to influence the quality of the final product.3-5) Thus, it is crucial that the drying method be controlled to assure that it does not adversely affect the quality of the final product.Common drying methods used in the pharmaceutical industry include hot air oven drying and fluid bed drying. These methods employ different modes of moisture removal and differ in drying capability. In recent years, microwave drying has gained greater interest. The moist material is subjected to the high frequency electromagnetic waves that selectively excite the polar molecules (dipoles) and ions causing them to align with the rapidly alternating electric field. Heat (dielectric heating) will be generated during the orientation of these dipoles and ions that in turn evaporates the moisture present in the material. Thus, a pressure gradient is created and it promotes the rapid removal of liquid water and water vapour towards the surface of the material.6-9) Basically, the principle of dielectric heating involves the absorption of energy by dipoles and the energy absorbed is given by:where P ϭenergy absorbed f ϭmicrowave frequency E ϭelectric field E 0 ϭdielectric constant of vacuum E r ϭdielectric constant of material tan dϭloss tangent tan d can be regarded as a measure of the molecular interaction. The product of the dielectric constant, E r and tan d is the loss factor and it determines the energy absorbed and thus the heating rate. McLoughlin and other coworkers found that the moisture content variation within the material undergoing drying with microwave was lower than a conventionally dried product. 8) Thus, microwave drying is especially useful for moisture-sensitive materials.In addition, the microwave drying technology is useful for production of very high potency dosage forms because it provides the possibility of drying in the same production container. Thus, it reduces the likelihood of cross contamination and human contact with the high potency drug. Furthermore, such a single-pot process also reduces the number of equipment used for production and its associated cleaning and validation activities.Various authors have investigated the influence of equipment parameters and the effects of dielectric properties of materials in microwave drying. 8,10,11) It was reported that localised heating could arise in microwave drying and be overcome with bed agitation. With respect to the influence on granular properties, Mandal found that microwave radiation did not modify the surface properties and dissolution rates of...

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