Product flowability, spray dried particles

Microcrystalline Cellulose. Microcrystalline cellulose is a purified, partially depolymerized cellulose that occurs as a white, odorless, tasteless, crystalline powder composed of porous particles. It is widely used in pharmaceutical dosage forms, primarily as a filler-binder in oral tablets and capsules with both wet granulation and direct compression processes. Microcrystalline cellulose was marketed first in 1964 by the FMC Corporation under name Avicel PH in four different particle size grades, each with different properties.37 Addition of Avicel into a spray-dried lactose-based formulation overcame compressibility problems. At the same time, the lactose enhanced the flowability of the Avicel products available at that time. The direct compression tableting process became a reality, rather than a concept, partially because of the availability of Avicel. As of 2007, Avicel PH is commercially available in 10 types with different particle size, density, and moisture grades that have different properties and applications (Table 7.6).38 Other brands of microcrystalline cellulose are also available on the pharmaceutical market, including Pharmacel 101 and 102 from DMV International and Emcocel 50 M and 90 M from JRS Pharma. 

Since the choice of the atomizer is very crncial, it is important to note the key advantages and limitations of different atomizers (centrifngal, pressnre, and pneumatic atomizers). Other atomizers, e.g., ultrasonic atomizer, can also be nsed in spray dryers (Bittern and Kissel 1999) but they are expensive and have rather low capacity. Although different atomizers can be used to dry the same feedstock, the final product properties (bulk density, particle size, flowability, etc.) are quite different and hence a proper selection is necessary. 

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