Tablet manufacture microcrystalline

Microcrystalline cellulose - mainly used as a binder or diluent in solid oral dose formulations. It also has lubricant and disintegrant properties which make it a useful excipient in tablet manufacture. 

Different localized levels of molecular order can coexist in some pharmaceutical materials, giving rise to the occurrence of partially crystalline (and partially amorphous ) systems. In most cases, the properties of such materials (e.g., density) are intermediate to those of the 100% amorphous and 100% crystalline samples. By deliberately varying the level of crystallinity in such systems, their properties can be customized for a particular purpose. An example of this is with the tableting excipients microcrystalline cellulose and spray-dried lactose, which have had their compression characteristics optimized by manipulating their amorphous content. The properties of partially crystalline materials may be approximated in many instances by making physical mixtures of the totally amorphous and crystalline samples. This is known as the two-state model for partially crystalline systems.However, such experiments should be undertaken with caution as the mixed two-state material can sometimes have significantly different properties from the partially crystalline material that is manufactured directly (the real one-state system). ... 

The effect of particle size reduction on the bioavailability of nitrofurantoin was shown in Fig. 4. The microcrystalline form (< 10 pm) is more rapidly and completely absorbed from the tablet dosage form than is the macrocrystalline form (74-177 pm) from the capsule dosage form. This is not a completely satisfactory illustration of the effect of particle size on the rate and extent of availability, since other manufacturing variables have not been held constant. Nevertheless, it does suggest some correlation between particle size, dissolution rate, and rate of availability. 

For the pharmaceutical product development scientist, there is clearly a need for objective information about the practical performance of different excipients and their various grades. In this chapter we set out to bring together the results of some of our ongoing evaluations of the physical and mechanical properties of excipients commonly used for the manufacture of solid oral dosage forms. In this particular article, we have chosen to focus on the fillers that are most commonly used in the manufacture of immediate release tablets microcrystalline cellulose (MCC), lactose, calcium phosphate, and mannitol (1). 

Fig. 20 Compression force vs. hardness plots for microcrystalline cellulose tablets with 0.07 and 5.1% MC. (The points represent individual tablets collected during manufacture.)...

In a very recent study, fluidized bed manufactured, enteric-coated, omeprazole pellets compressed into tablets were analyzed using neural networks.From the model, the authors were able to predict a positive correlation between the tablet strength and the concentration of the microcrystalline cellulose used as a compression aid. However, the degradation of the omeprazole in such media was also dependent on the microcrystalline cellulose concentration. 

Most direct compression diluents are available from only one source, but a few can be obtained from more than one manufacturer. If multiple sources are available, they will be offered under individual registered names. For example, microcrystalline cellulose is available under a number of brand names such as Avicel (FMC Corporation), Emcocel (Edward Mendell), and Vivacel (J. Rettenmaier). Chemical properties of such materials will be similar if not completely identical, especially if there are pharmacopeial standards for identity and purity. However, it cannot be assumed that products from different manufacturers will have the similar physical properties which will govern their performance in the tabletting process. 

The tablet mass was fixed at 200 mg. Each unit contained 10 mg (5%) drug and 1.2% lubricant. It was considered that the lubricant level could be adjusted and optimized later as part of a process study. Thus, although there were 5 components in the mixture, 2 of them were fixed. The factor space in the remaining components, microcrystalline cellulose, lactose, and carbomer (totalling 93.8%) can be represented as a ternary diagram. The tablets were manufactured by direct compression of the powder mixture and the dissolution profiles were measured at pH 2 (0.01 M hydrochloric acid) and pH 7 (phosphate buffer). The time for 50% dissolution was measured in each case. 

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