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fact, these must be intrinsic excipient qualities. Table 1 lists examples of how several material attributes relate to func- tional properties. Excipients that perform inadequately can cause segrega- tion that leads to poor content uniformity, inconsistent tablet weights, inferior tablet strength and, ultimately, dis- solution failure. Preventing these deficiencies requires excipient combinations that balance flowability and com- pressibility, and several manufacturers offer co-processed excipients to do just that. Table 2 lists some of them. Benefits of DC-grade HPMC The recent introduction of a DC-grade hydroxypropyl methylcellulose (HPMC) 2208 is a significant step in facili- tating the task of formulators, especially to create modified- release (MR) forms. That's because HPMC-based hydrophilic matrix tablets constitute a significant percent- age of all MR solid oral dosage forms [1]. The benefits of HPMC-based MR tablets include versatility in accommo- dating active pharmaceutical ingredients (APIs) that have a wide range of physicochemical properties. Such tablets are also simple to design, easy to manufacture, and inexpensive. In conventional form, HPMC is a fine powder with a fibrous morphology that benefits a tablet's mechanical properties. Its fibrous nature, however, limits flowability and can make it difficult to use in DC processes. However, the new DC-grade HPMCs—Benecel PH DC from Ashland and Methocel DC2 from Dow—have particles whose morphology improves flowability. These superior attributes help formulators delineate the critical process parameters (CPPs) and streamline the complex interplay between product and process. This has become even more important since the FDA introduced its Quality by Design (QbD) and other initiatives, which have prompted phar- Figure 1 Process flow of wet granulation, dry granulation, and direct compression Wet granulation Raw materials Dry granulation Direct compression Drying Milling Roller compaction Wet massing Tablet compression Blending lubrication Screening Raw Materials Tablet compression Blending lubrication Dry screening Screening Raw Materials Tablet compression Blending lubrication Dry screening Wet screening Screening Table 1 Potential impact of material properties on quality attributes and processing behavior Material attributes Functional properties Flowability Blending Mechanical properties Partical size distribution X X X Particle shape X - - True density - - X Bulk density X X X Particle surface area X X X Particle surface energy X X - Cohesiveness X X - Brittleness/elastic modulus - - X Table 2 Brand names and composition of some co-processed excipients used in solid dosage forms Brand name Composition (percentages) Advantose FS Fructose-starch (95-5) Avicel CE 15 Microcrystalline cellulose (MCC)-guar gum (85-15) Avicel CL-611 MCC-sodium carboxylmethyl cellulose (85-15) Avicel RC-591 MCC-sodium carboxylmethyl cellulose (89-11) Barcroft CS90 Calcium carbonate-starch (90-10) Cellactose α-Lactose monohydrate-powder cellulose (75-25) Compressol S Mannitol-sorbitol (70-30) Di-Pac Sucrose-maltodextrin (97-3) Effer-Soda Sodium bicarbonate-sodium carbonate (90-10) ForMaxx Calcium carbonate-sorbitol (70-30) LudiFlash Mannitol-polyvinyl alcohol-crospovidone (90-5-5) Microcellac α-Lactose monohydrate-MCC (75-25) Pharmatose DCL40 β-Lactose-anhydrous lactitol (95-5) ProSolv SMCC50 MCC-colloidal silicon dioxide (98-2) StarCap Corn starch-pregelatinized starch (90-10) StarLac 100 α-Lactose monohydrate-corn starch (85-15) SugarTab Sucrose-invert sugar (93-7) Timerx Xanthan gum-locust bean gum (??-??) Xylitab 100 Xylitol-polydextrose (96.5-3.5) Xylitab 200 Xylitol-sodium carboxylmethyl cellulose (98-2) Tablets & Capsules September 2015 15