Tablet quality

Introduction In order to assure constant tablet quality, the following requirements apply ... 

The effect of raw material variability on tablet production [2,30,31] and suggestions for improving tableting quality of starting materials [21] has been the subject of several publications. Table 3, which lists the characteristics of different sources of magnesium stearate, clearly illustrates the variability of this material [32]. Phadke and Eichorst have also confirmed that significant differences can exist between different sources, and even different lots, of magnesium stearate... 

Table 6 Influence of Spray Pattern Used on Tablet Quality...

All too often, an overly simplistic view is taken of the role that spray gun design (namely, brand of gun, and features of the fluid nozzles and air caps used) can play in achieving good, and reproducible, coated tablet quality. The fact that spray gun design may differ (from laboratory to production setting) is often considered to have little relevance, and accommodations for such differences are routinely made based on prior experience and, often, instinct, without benefit of reference to scientific data. A commonly held assumption, therefore, is that guns made by one manufacturer are... 

TABLE 6.22 Influence of Tablet Physical Properties on Tablet Quality Attributes... 

Tablet Physical Property Tablet Quality Attribute...

Picker-Freyer, K. M., and Schmidt, A. G. (2004), Does temperature increase induced by tableting contribute to tablet quality /. Therm. Anal. Cal., 77,531-539. 

A very novel application of neural networks recently reported was that of maximizing tablet yield in a production environment. The authors analyzed a data set of 100 typical batches of tablets, classified and rated the inputs according to their importance (influence on tablet yield) and used a neural network model to maximize tablet yield while holding tablet quality within specified limits. 

Upon proper die fill, one must consider whether the material will form a tablet. The tableting characteristics of powders depend on the viscoelastic properties of the material. The process of compaction has been defined as the compression and consolidation of a two-phase system due to an applied load. The quality of the compact depends on the compression and consolidation of the powder mass, decompression of the compact, ejection from the die, and subsequent scrape-off from the lower punch. A schematic representation of the compression process is shown in Fig. 1. Because these viscoelastic properties are time dependent, both the magnitude and the rate of application (and release) of the compression force affect tablet quality. 

After the compression and consolidation of the powder in the die, the formed compact must be capable of withstanding the stresses encountered during decompression and tablet ejection. The rate at which the force is removed (dependent on the compression roller diameter and the machine speed) can have a significant effect on tablet quality. The same deformation characteristics that come into play during compression play a role during decompression. 

Tablet jams and chipping at the stripper reduce tablet quality and may contaminate the feeder resulting in weight variation. High speed machines typically have greater problems than slower machines. These problems are solved by focusing on the tablet stripper and lower punch ejection height.

It has long been known that for some formulations, changing the speed of operation of the tablet press or changing the type of press can have a profound effect on tablet quality. Such circumstances may arise, for example, when changing from a slow excentric press in formulation development to a high speed rotary in production. 

The magnitude of the effect that a given active ingredient will have on tablet properties will clearly depend on the tabletting properties of that substance. If it is also capable of direct compression, then the effect will not be great. If, however, it is a substance that is difficult to compress into tablets, then it will cause a marked deterioration in tablet quality when mixed with the diluent. Therefore, for a reliable test of capacity, the direct compression diluent should be mixed with a standard substance and tabletted under standardized conditions. The pressure-strength profiles of the mixtures can then be constructed. Paracetamol and ascorbic acid have been used as standards. 

A faulty batch of tablets can sometimes be recovered by grinding up the tablets and recompressing them, a process which is known as reworking and is analogous to the dry granulation method of tablet manufacture. This can sometimes cause problems with a direct compression formulation. Many direct compression diluent particles are in the form of aggregates, e.g., spray-dried lactose is composed of small crystals of lactose embedded in amorphous lactose. If these aggregates are compressed, their structure may be broken down to such an extent that subsequent recompression will result in impaired tablet quality. 

At the same time, the more traditional tabletting techniques in the pharmaceutical industry were improved and modernized which led to higher production capacities, better tablet qualities, as well as more variability in product shape and composition. Other agglomeration methods were also introduced such as fluidized and spouted beds, mixers of various kinds, etc. 

Although the simplicity of the direct compression process is obvious, if pharmaceutical blends are pre-treated in one way or another prior to tabletting, flow characteristics can be improved, compressibility adjusted, and a good particle size and distribution can be selected that yields an optimal feed bulk density. However, the pretreatment of dry dosage formulations becomes more and more complicated to render them suitable for use with the sophisticated high-speed tabletting machines [B.34, B.41, B.48, B.66, B.71, B.97, B.99, B.105]. In simple terms, for those presses it is a requirement that the feed flows quickly and uniformly into the die cavities where it can be converted into well-shaped and firm compacts in a very short time. Tablet quality is a result of the blend s compressibility . This characteristic not only includes an excel-... 

Bandyopadhyay AK, Chaudhuri B, Bhattacharjee PK. Starch paste granulation I effect of dextrinized corn starch mucilage as binding agent on granulation and tablet quality. Aust J Pharm Sci 1980 9(3) 85-89. 

The tensile strength of tablets is routinely tested as a measure of tablet quality [2]. It is possible to consider three types of tensile strength - radial, bending, and axial. Here we discuss only the radial tensile strength as it is... 

Here, d is the tablet diameter and h the tablet thickness. It is the radial tensile strength that is commonly determined to assess tablet quality. Procipio et al. [5] have discussed measurement of radial tensile strength. 

---