The Effect of Mill Type on Two Dry-Granulated Placebo Formulations - Pharmaceutical Technology

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The Effect of Mill Type on Two Dry-Granulated Placebo Formulations
The authors evaluate the effect of various mill types on particle-size distribution, flowability, tabletability, and compactibility.

Pharmaceutical Technology
Volume 32, Issue 11, pp. 72-86

Table I: Microcrystalline cellulose–dibasic calcium phosphate (2:1) placebo formulation.
Gran-U-Lizer. The Gran-U-Lizer is a nonattrition size-reduction mill. It uses roller-mill technology that contols particle-size reduction through roll-surface texture (i.e., roll type), roll speed, and roll gap. According to MPE, the Gran-U-Lizer operates through the use of shear, in contrast to impact used by conventional size-reduction equipment. The Gran-U-Lizer achieves a narrower particle-size distribution with fewer fines by eliminating the attrition inherent in other milling designs. The laboratory model Gran-U-Lizer requires several passes through the rolls using various roll types, roll speeds, and roll gaps to achieve the desired particle-size distribution. All milling trials using the Gran-U-Lizer roller mill were conducted at MPE's Chicago site.


Table II: Microcrystalline cellulose–lactose (2:1) placebo formulation.
Two IR, dry-granulation placebo formulations (see Tables I and II) were selected to evaluate mill performance. Roller-compaction conditions were established using the Gerteis Mini-Pactor roller compactor to produce ribbon at a target solid fraction of 0.7 at an approximate thickness of 2.5 mm. Ribbon was manufactured from both formulations and characterized for solid fraction, tensile strength, and thickness. Roller-compaction bypass was measured to establish the fines level within the compacted ribbon before milling.

Ribbon characterization

Figure 1: Measurements of ribbon dimensions. (AUTHORS)
Solid fraction. Ribbon samples were prepared by cutting the compacted ribbon into rectangular shapes of approximately 10 x 22 mm using a jeweler's table saw. Figure 1 demonstrates how the ribbon sample was prepared. The cut ribbon sample was measured using calipers to determine the envelope density.

The solid fraction of each ribbon sample was determined according to a relationship that can be expressed by the following equation:

in which w is the ribbon width, l is the ribbon length, t is the ribbon thickness, m is the ribbon mass, V s is the volume of the roller serrations, and ρ t is the true density of the material.


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