Tablets weight uniformity

The prediction power of the shear cell measurement for powder flow as judged by tablet weight uniformity is shown in Figure 2. Discrepancies, especially among powders with good flow, are observed. 

Tablet weight uniformity will provide a measure of the efficiency of the powder flow, tlie force feeder, or the automated weight control system. Weight monitoring by the press operator is usually the weight of a 5- or 10-tablet sample. Uniformity of individual tablets, which after all does relate to dose, will be more informative. The powder flow may not be sufficiently good, even with forced feeders.

Simulation Approach The numerical simulations were carried out using program SIMGAUSS, see data file TABLET C.dat for content uniformity, respectively TABLET W.dat for weight uniformity. The mean weights and contents were varied over a range covering the nominal values. 

Evaluate the results from step 3. Comment on the uniformity of the tablet weight. Also note the milligrams of ibuprofen per tablet found on the label and compare this with your results. If the label value is less than the mean you calculated, give some possible reasons for this. 

Figure 2 Shear cell index versus weight uniformity from a B3B tablet press.

Despite the diligent use of predictive studies, compaction simulation, pilot scale work, the state of the art of tablet scale-up still provide opportunities for problems to arise. The issues typically encountered are those that have multiple factors involved, and are difficult to predict and simulate at smaller scale. Of these problems, tablet mixture flow, including weight uniformity and segregation, and sticking and picking of the tablet mixture to the tools and tablet specks, are common occurrences. 

During scale-up of a bilayered tablet, it is necessary to determine the range of tamping that can be tolerated for a product. Typically, the tamping force and overall compression force are varied and the tendency to laminate is observed. In addition, the other tablet characteristics are also determined, e.g., hardness, thickness, weight uniformity, disintegration, and dissolution. 

The Tandem system (Bruker Optics) is available for use during tablet production to measure tablet weight, thickness, hardness, and diameter, as well as online NIR content uniformity. The system can provide online analysis for drug substance uniformity, moisture content, and excipients. The advantage of systems like this is that the necessary data are available immediately to make adjustments to the production parameters in order to improve product rmiformity. Therefore, adjustments can be made to tablet weight in real time in order to achieve 100% of the label claim. 

Tablet weight, hardness, thickness, content uniformity, friability, dissolution, disintegration, Assay/ potency...

The major use of the instrumented press in the operations or production area is for tablet weight monitoring and control. Early research in this field was able to show that the measured force of compression was proportional to the mass of material in the die cavity. This, of course, led to systems that could monitor the uniformity of the peak heights measure, send a signal to a servo motor on the press to adjust the weight control if necessary, and finally turn off the press or... 

Greater weight uniformity is achieved with coarse powders or granules as feed. Too large a proportion of fines may cause the tablets to come apart upon ejection. Satisfactory feed can be prepared by first making large tablets in another machine and then... 

Tableting Weight Hardness Thickness Disintegration and/or dissolution Friability Potency Dosage uniformity Degradants...

Figure 3 Histogram of drug A granulation uniformity resulting from different blending times. Percentage of relative potency = (tablet assay/tablet weight) X 100.

Compression is a critical step in the production of a tablet dosage form. The materials being compressed will need to have adequate flow and compression properties. The material should readily flow from the hopper onto the feed frame and into the dies. Inadequate flow can result in rat holing in the hopper and/ or segregation of the blend in the hopper/feed frame. This can cause tablet weight and content uniformity problems. As for the compressibility properties of the formulation, it should be examined on an instrumented tablet press. Factors to consider during compression are as follows ... 

Appearance Hardness Tablet weight Friability Disintegration Weight uniformity... 

When manufacturing a tablet formulation by direct compression, the particle size and size distribution of excipients have a significant impact on blending homogeneity, powder segregation, and flowability. This can result in unacceptable content uniformity and high tablet weight variation. In such situations, control of excipients can be critical to product quality. 

First, the die is filled when it passes beneath a stationary feed frame and the lower punch is in the filling position. Tablet weight variation is dependent on uniform powder filling into the die cavity. Since the residence time of the die under the feed frame is very short, the formulation blend must flow easily and reproducibly. 

Special dedicated hardness testers or multifunctional systems are used to measure the degree of force (in kilograms, pounds, or arbitrary units) required to break a tablet. Devices to test tablet hardness include the Monsanto tester, the Strong-Cobb tester, the Pfizer tester, the Erweka tester, and the Schleuniger tester. A force of about 4 kg is considered the minimum requirement for a satisfactory tablet. Multifunctional automated equipment can determine tablet weight, hardness, thickness, and diameter. Unfortunately, these testers do not produce uniform results for the same tablet due to operator variation, lack of calibration, spring fatigue, and manufacturer variation. 

The systems to control weight uniformity are not able to control uniformity of the mixture. When during filling of the die the tableted material demixes, tablet weight... 

---