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Sample Size same material compressed under conditions identical to
those of thinner tablets, with the same tooling shape and to In order to achieve sufficient
statistical precision for the the same peak force, will require greater breaking forces.
determination of average breaking force, a minimum of 6 Tablet orientation and failure should
occur in a manner con- tablet samples should be tested. The average breaking force sistent with
those used during the development of the dos- alone may be adequate to fulfill the purpose of
process or age form. For direct comparisons (i.e., without any normal- product quality control. In
cases where breaking force may izations of the data), breaking force measurements should be
particularly critical, the average plus individual breaking be performed on tablets having the
same dimensions, ge- force values should be accessible.
Non-Pharmacopoeial or Non-Official Tests
These are tests that are performed on tablets and which are not listed in official compendia and concern a variety of
quality attributes that need to be evaluated, such as the porosity of tablets, hardness or crushing strength test,
friability test, tensile strength determination, thickness test etc.
Some of these tests have no officially set limits for acceptance or rejection and thus may vary from manufacturer to
manufacturer and from formulation to formulation.
Crushing strength and friability appeared in the 2001 Edition of British Pharmacopoeia (Appendix A324). There was
however no definite set limits. The two tests are, therefore, here considered under non-pharmacopoeial tests.
Tablet Hardness or Crushing Strength Test
This measures the degree of force (in kilograms, pounds, or in arbitrary units) needed to fracture a tablet. Besides the
concentration of binders used and the compression force, the hardness of a tablet depends on
The characteristics of the granules to be compressed e.g., hardness and deformation under load.
The type and concentration of lubricant used and
The space between the upper and lower punches at the time of compression.
The crushing strength of tablets is usually checked using Monsanto or Stokes hardness tester, Strong-Cobb
hardness tester and the Pfizer crushing strength tester. All are manually used. So, strain rate depends on the
A force of about 4 kg is considered the minimum requirement for a satisfactory tablet. Measurement is usually carried out using a
minimum of ten tablets
Where F is the force needed to fracture a cylindrical flat-faced tablet of thickness t along its diameter D.