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M 14 October 2014 Tablets & Capsules excipients Assessing how the physical properties and enhanced powder flow of HMPC affect process control during direct compression of matrix tablets True L. Rogers, Kathryn O. Hewlett, Jörg Theuerkauf, Karen M. Balwinski Dow Pharma & Food Solutions Madhusudhan Kodam Dow Chemical This article describes a study that investigated a new direct- compression grade of HPMC alongside a control. The study characterized the differences in the physical properties of the two HPMCs and assessed whether those differences—as well as flow performance—translated into differences in the processabil- ity of matrix tablets. ore than 75 percent of modified-release oral solid dosage forms are hydrophilic matrix tablets [1]. These tablets represent a primary formulation option because they are relatively easy to develop and inexpensive to manufacture. Hydroxypropyl methylcellulose (HPMC) is the polymer of choice to make these tablets perform as modified-release drug delivery systems. HPMC is derived from cellulose, a renewable re - source. It is considered a hydrophilic, non-hygroscopic polymer and is commonly used in matrix tablets because it swells upon contact with aqueous media and eventually fully dissolves. This behavior is key to the formation of the hydrated, swollen layer that surrounds the HPMC matrix tablet following administration and that modulates release of the active pharmaceutical ingredient (API) via diffusion and erosion. Dry HPMC typically exhibits a fine, fibrous morphology, which benefits a tablet's tensile properties but causes the powder to flow poorly. Most APIs also flow poorly, so wet granulation is commonly employed to make formulations easier to process. Figure 1 illustrates the process typically used to manufacture matrix tablets via wet granulation, usually in batches using a high-shear or fluid-bed granulator. Continuous processing and direct compression There is an industry-wide shift from batch to continu- ous processing [2-4], and roller compaction is considered a continuous dry granulation technique that is increas- ingly used as an alternative to high-shear and fluid-bed granulation [5]. Like wet granulation, roller compaction improves a formulation's processability and reduces segre- gation of its components; it also eliminates the need for solvents. Furthermore, dry granulation entails fewer pro- duction steps than wet granulation, thus improving effi- ciency and reducing production costs [6]. Roller com- paction also prevents degradation of moisture-labile or heat-sensitive APIs, which may be another reason for the increase in its use. One of the challenges of roller com-