Properties of Coprocessed Excipients

The subject of coprocessing of excipients is multifaceted, with the following characteristic properties. 

Coprocessing provides a multitude of improvements in the product s functionality, the most notable of which are discussed below. 

Controlled optimal particle size and size distribution ensures superior flow properties of coprocessed excipients and reduced reliance on addition of glidants. The volumetric flow properties of SMCC were studied in comparison with those of the physical mixture of its parent excipients (42). The particle size range of the two test samples was found to be similar, but the flow of coprocessed excipient was better than that of the physical mixture. A comparison of the flow properties of Cellactose with its parent excipients was also performed (5) by measuring the angle of repose and Hausner ratio, and Cellactose was found to have better flow characteristics than lactose or a physical mixture of cellulose and lactose. The spray-dried coprocessed product had a spherical shape and even surfaces, which resulted in improved flow properties. On similar terms, mechanically coating the 2% CSD over microfine cellulose powder resulted in improving its flow properties (43). 

The most common problem manifested due to poor flow property is the variation in fill weight. This problem is much more serious in the case of DC excipients, but coprocessed excipients are devoid of this effect, when compared with the physical mixture of their parent excipients. This is because of the impregnation of one particle into the matrix of another, which reduces the rough particle surfaces and creates a near-optimal size distribution, causing better flow properties. Tablets prepared with M80K, a coprocessed cellulose powder with CSD, showed lesser weight variation than those prepared with Avicel (43). 

Fill-weight variation tends to be more prominent with high-speed compression machines. This phenomenon was studied with various machine speeds for SMCC and MCC, and the former showed lesser fill-weight variation than the latter (44). 

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Coprocessed excipients have been mainly used in DC tableting because of their better flow ability and compressibility, and the excipient formed is a filler-binder. The compressibility of several coprocessed excipients such as Cellactose (45), SMCC (42,44), and Ludipress (BASF AG, Ludwigshafen, Germany) (46) have been reported to be superior to the physical mixtures of their constituent excipients. While comparing the compressibility profile of SMCC with MCC in the presence of high compression forces, the former was found to retain the compaction properties,... 

Offer improvement in organoleptic properties, such as those in Avicel CE-15 (FMC BioPolymer, Newark, Delaware, U.S.A.), a coprocessed excipient of MCC and guar gum, designed for providing chewable tablets with reduced grittiness and tooth packing, minimal chalkiness, better mouth feel, and improved overall palatability. 

Coprocessed tablet excipient composed of chitin and silicon dioxide [52] Chitin is a water-insoluble hydrophilic polymer that can absorb water and function as a disintegrant. Due to the unacceptable flow and compression properties of chitin, coprecipitation with silicon dioxide was used to provide a new excipient with excellent flow, compaction and disintegration properties when compared to the individual components or commercially available direct compression fillers and disintegrants. The optimal composition of the coprocessed excipient contains a silicon concentration of about 50% (w/w). 

FIGURE 2.47 Physical properties of the coprocessed mannitol-chitin excipient compared with commercially available ODT excipients. 

Although DC seems to be the method of choice for tableting, wet granulation is still widely used in various product manufacturing. Excipients such as MCC lose compressibility upon addition of water, a phenomenon called quasi-hornification (49). This property is improved, however, when it is coprocessed into SMCC. 

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