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40 May/June 2021 Tablets & Capsules ment by reducing tablet compaction pressure, a necessity given the unin- terrupted nature of CM operations. The powder flow characteristics of SMCC are especially impressive, dwarfing those of ordinary MCC. As depicted in Figure 2, SMCC registers flow function values well above 10, which is the mark for being consid- ered "free flowing" after analysis in an FT4 powder rheometer. This degree of powder flow has important impli- cations for direct compression, in which blending, lubrication, tablet compression, collection, and charac- terization must all be considered. A sensitive issue Lubricant sensitivity can be a problem for CM, especially if limits are placed on when materials can be added. IFF's proprietary SSF offering (Alubra) has been shown to improve tablet tensile strength and lower friability without interfering with disintegration time. A lubricant that is less sensitive to prolonged mix- ing—such as one-step mixing—while sustaining these properties is invalu- able in the nonstop stream of CM. IFF researchers compared six batches of tablets in a recent case study—the first three were lubricated with SSF and the remaining three with magnesium stearate (MgSt). For all batches, ingredients were added simultaneously to a v-blender for mixing at intervals of 10, 20, and 30 minutes. As Figures 3 and 4 clearly show, the batches lubricated with SSF yielded better tensile strength, quicker disintegration time, and lower friability than their MgSt- containing counterparts. Granulation and milling Much like the feeding and blend- ing stage, a streamlined granulation and milling process depends on opti- mal particle morphology to avoid adhesion and attrition. Tablets man- ufactured through CM often go through a continuous wet granulation process, so excipients that can spend less time being saturated—and there- fore less time drying—are preferable. IFF researchers have determined that a high-density microcrystalline the CR material, resulting in a higher number of tablets produced. Our research has also shown that silicified microcrystalline cellulose (SMCC)—a co-processed blend of MCC and colloidal silicon dioxide— possesses the necessary qualities to improve powder flow. In addition, SMCC performs favorably in terms of compactability and binding, both of which contribute to robust for- mulations that tend to be uniform in content. This unique excipient also reduces wear on tooling equip- Researchers conducted a case study to test the advantages of HPMC for the production of minitablets. Two batches of 2-millimeter minitablets were produced at 80 rpm using multi- tip tooling. One batch contained DC2, while the other used cellulose ether HMPC (Methocel CR HPMC). As shown in Table 1 and Figure 1, the batch made with DC2 produced more tablets within the target weight range with lower variability. In addition, the DC2 material reduced the number of process interruptions compared to Figure 2 Flow characteristics by FT4 powder rheometer 15 10 5 0 Avicel PH 101 Avicel SMCC 50 Avicel PH 102 Avicel SMCC 90 Avicel PH 302 Avicel SMCC HD90 Flow function (3 kilopascals) Figure 1 Weight of minitablets CR grade DC grade Minitablet weight (milligrams) 8.0 7.8 7.6 7.4 7.2 7.0 6.8 6.6 6.4 6.2