Issue link: https://www.e-digitaleditions.com/i/1371139
30 May/June 2021 Tablets & Capsules For all tablets in the example data set, the elastic recov- ery values are acceptably low (less than 3 percent). Lubrication data A full lubrication evaluation requires two measure- ments, as shown in Figure 3. Ejection force is the force required to push the tablet out of the die. Take-off force, or detachment force, is the force needed to detach the ejected tablet from the lower punch tip. Both measure- ments are used to evaluate the formulation's lubrication status. Higher forces indicate poor lubrication and an increased risk of sticking and picking. Force values are converted to stress data to account for tablet dimensions. Maximum ejection and detachment stresses of 3 megapas- cals are generally recommended, but maximum acceptable stresses as low as 1 megapascal can be recommended for products that are particularly prone to sticking. As shown in Figure 4, the detachment and ejection stress values for all example tablets were acceptably low, indicating that all three blends were well lubricated. The lubrication stresses were largely independent of com- paction pressure, which is typical for well-lubricated formulations. Although the ejection stresses for Formula 1 were somewhat higher than the other variants, they were well within the acceptable range. No lubrication prob- lems would be anticipated for these formulations. Having assessed the results of the evaluation, we can draw the following conclusions: • The rank order of the formulations' compactibility is F2>F1>F3. • None of the formulations reach the critical tablet- ability threshold. Even F2 would benefit from improved tabletability. • All formulations are well lubricated. Based on these observations, and assuming that the processing properties of all the products were acceptable, then Formulation 2 would be selected for further work. To improve the formulation's tabletability, developers could consider adding a compression aid such as microcrystal- line cellulose, changing an excipient in the formulation to a more compressible grade, or adjusting the lubrica- tion (by reducing the lubricant concentration or blending time). The developers could then quickly see the impact of such changes by repeating the analysis, allowing for rapid formulation development with minimal outlays of time and materials. T&C Michael J. Gamlen is chief scientific officer and Rebecca U. McVicker is product director at Gamlen Tableting (+44 0 115 912 4271, www.gamlentableting.com). The company manu- factures a range of advanced powder compaction analyzers, which can be combined with its Gamlen Dashboard software to create the first fully automated compaction analysis system. Figure 4 Example lubrication data of three formulations Formula 1 Formula 2 Formula 3 Good Borderline Poor a. Detachment stress profile Detachment stress (megapascals) 0.6 0.5 0.4 0.3 0.2 0.1 0.0 Compaction pressure (megapascals) 0 50 100 150 200 250 b. Ejection stress profile Ejection stress (megapascals) 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Compaction pressure (megapascals) 0 50 100 150 200 250 Figure 3 Lubrication measurements Detachment force Ejection force