Lubrication of Direct-Compressible Blends with Magnesium Stearate Monohydrate and Dihydrate - Pharmaceutical Technology

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Lubrication of Direct-Compressible Blends with Magnesium Stearate Monohydrate and Dihydrate
The influence of magnesium stearate (MgSt) on powder lubrication and finished solid-dose properties presents big challenges to drug manufacturers.

Pharmaceutical Technology

Table IX: Postlubrication of MCC–LAC binary diluent systems with different MgSt types.
Influence of type and concentration of MgSt hydrate on tablet compression. The tablet characteristics shown in Table VI depict some distinct effect in the total compression forces, ejection force, and tablet knock-off between the blends lubricated with different pseudopolymorphic forms of MgSt. These differences in tableting forces appear to be evident under similar formulations and with preset target ranges for tablet weight and hardness. So long as the preblend components of the formula are comparable, the anticipated variables would include percentage of MgSt and duration of lubrication. These two variables tend to influence the compressibility, tablet ejection, and knock-off. The efficiency of a lubricant during a tableting operation hinges on its ability to facilitate tablet release postcompression. The amount of such lubricants, however, combined with the duration of lubrication, often influence the forces acting on the upper and lower punches. The results indicate that the average total compression forces and ejection force was lower for MgSt-D than the MgSt-M (see Table VI and Figures 10 and 11).

Figure 10
The varying effects of MgSt on formulations with various types of diluents were previously observed by Swaminathan, Simmons, and Bourland (23). They concluded that MgSt when used as an intragranular agent in a roller compaction process had greater effect on tablet tensile strength of viscoelastic formulations (such as LAC) than on intermediate or brittle formulations (such as DCP). Although the role of MgSt as an extragranular agent is well understood, the results from compression process of the current study indicate that regardless of the MgSt type, formulations that contained an MCC–LAC diluent system required lower compression and ejection forces than those that contained an MCC–DCP diluent system to produce tablets with desired quality attributes (see Table VI). More important, and on the basis of tablet characteristics, blends lubricated with the MgSt-D appear to require lower compression and ejection forces to produce comparable tablets as those containing MgSt-M. With respect to the lubricated blends, the profiles show that less densification occurs when the dihydrate was used than when the monohydrate form was used. Such disturbance in blend homogeneity as a result of the introduction of lubricants such as MgSt, if not monitored and controlled, could portend blend or product failure.

Figure 11
In vitro dissolution: binary diluent systems. In vitro dissolution was conducted on six tablets from each of batches 1, 7, 10, 11, 12, and 14. These batches were lubricated with different amounts of MgSt-M and MgSt-D ranging from 0.3% to 1.0%. Figure 12 shows results from Batch 1 and Batch 10 lubricated for 10 min with 0.3% MgSt-M and MgSt-D, respectively. Figure 13 shows results of Batch 7 and Batch 11 lubricated for 4 min with 1.0% MgSt-M and MgSt-D, respectively. And Figure 14 shows results from Batch 12 and Batch 14 lubricated for 4 min with 1.0% MgSt-M and MgSt-D, respectively. Results of the in vitro dissolution suggest that all batches met the criteria for similarity (f2 between 50 and 100) as stipulated in the FDA guidance (see Figures 12–14 and Table X). These results indicate that finished products containing the dihydrate polymorph could provide comparable quality to those containing the monohydrate form.


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