Tablet testing hardness

The test for disintegration is performed as described in the USP, and the results are rounded to the nearest half-min. Disintegration time varied over a narrow range for all batches studied. The 15-batch average for the tray dryer process (2.7 min) is well below the specification (10 min) for this test. Hardness of tablets from the tray dryer process averaged 15 Strong-Cobb units (SCU). All batches exceeded the minimum specification (9 SCU) there is no upper... 

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. 

Hardness and friability tests are two additional tests usually performed as in-process controls during manufacturing. They will be required for product release when the characteristics of hardness and friability have a critical impact on the quality of the product. Carbamazepine is also available as a chewable tablet and because the hardness is an important characteristic of the tablet, a hardness test is required for batch release. 

For tablets and hard-gelatin capsules, the following specific tests are generally applied ... 

Fig. 5.32 Photograph of the Schleuniger Autotest 4" tablet testing system for the quick and automatic measurement of tablet weight, thickness, diameter, and hardness (courtesy Dr. Schleuniger Pharmatron, Manchester, NH, USA).

Initial Situation An experimental granulation technique is to be evaluated a sample of tablets of the hrst trial run is sent to the analytical laboratory for the standard batch analysis prescribed for this kind of product, including content uniformity (homogeneity of the drug substance on a tablet-to-tablet basis, see USP Section (905)" ), tablet dissolution, friability (abrassion resistance), hardness, and weight. The last two tests require little time and were therefore done first. (Note Hardness data is either given in [kg-force] or [N], with 1 kg = 9.81 Newton). 

The Erweka and Schleuniger testers operate on a counterweight principle that eliminates fatigue, if not frictional, losses. The latter of these two devices is supplied calibrated and a mechanical tablet is available for periodic recalibration. More recently, testers have been introduced that measure the load being applied to the tablet by means of load cells and therefore facilitate direct electronic digital readout. This eliminates the two major sources of error referred to above and permits recording of production of hard copies of the test results. 

Indentation hardness using modified tests based on Brinell hardness measurements have been used by some researchers [148] to provide information on the surface hardness of tablets. In addition, these tests are capable of providing a measure of a tablet s plasticity or elasticity. For the most part, such tests have been confined to basic research applications in a few laboratories, but their value is beginning to be more widely recognized. 

Hard gelatin capsules are uniquely suitable for blinded clinical tests and are widely used in preliminary drug studies. Bioequivalence studies of tablet formulations may be conveniently blinded by inserting tablets into opaque capsules, often along with an inert filler powder. Even capsule products may be disguised by inserting them into larger capsules. 

J.D. Kirsch and J.K. Drennen, Nondestructive tablet hardness testing by near-infrared spectroscopy a new and robust spectral best-fit algorithm, J. Pharm. Biomed. Anal., 19(3-4), 351-362 (1999). 

K.M. Morisseau and C.T. Rhodes, Near-infrared spectroscopy as a nondestructive alternative to conventional tablet hardness testing, Pharm. Res., 14(1), 108-111 (1997). 

M. Blanco, M. Alcala, J.M. Gonzalez and E. Torras, A process analytical technology approach based on near infrared spectroscopy tablet hardness, content uniformity, and dissolution test measurements of intact tablets, J. Pharm. Sci, 95, 2137-2144 (2006). 

M. Blanco, M. Alcala, Content uniformity and tablet hardness testing of intact pharmaceutical tablets by near infrared spectroscopy. A contribution to process analytical technologies. Anal. Chim. Acta, 557, 353-359 (2006). 

Compression force/hardness profile The compression/hardness profile of a granule batch is an important property. Different subunits of two formulations were selected and compressed using different compression forces in order to obtain tablets. The tablets were tested for hardness as a function of different subrmit numbers (Figs. 11,12). From experience, it is well known that certain formulations show an excellent compression profile as small batches but do not keep this property on the batch size increasing. This is another advantage of the quasi-continuous production concept as, in principle, the quality of the small batch is not changed by the repetitive procedure. 

Compacts were milled and final blends were compressed into tablets (Table 8 gives resultant powder properties). Tablets were tested for friability, thickness, hardness, and drug release. 

Disintegration time and tablet hardness data could be collected from the manufacturing batch records however, for ease of administration these figures will be obtained from the quality control test results, which also contain individual tablet weighings. 

Disintegration, too, can be influenced by hardness of the tablet. For these reasons, hardness testing results also will be examined. 

Obtaining test data to determine the numerical range of each parameter e.g., assess the tablet hardness over a series of batches that achieves an acceptable friability, disintegration, and dissolution. 

Tablet hardness is a property that, when measured, destroys the sample. The destructive nature of the test, coupled with the variability of the test itself does not contribute to an incentive to test a large number of samples. Morisseau and Rhodes99 correlated the diffuse reflectance NIR spectra of tablets pressed at different pressures and subsequently tested the tablet hardness with an Erweka Hardness Tester. The tablet hardness, as predicted by the NIR method, was at least as precise as the laboratory test method. Kirsch and Drennen100 evaluated NIR as a method to determine potency and tablet hardness of Cimetidine tablets over a range of 1-20% potency and 107-kPa compaction pressure. Hardness at different potency levels was used to build calibration models using PCA/ principal component regression and a new spectral best-fit algorithm. Both methods provided acceptable predictions of tablet hardness.

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