Evaluation of Structural Strength of Semisolids Conforming to USP 915 and USP 1912 by Penetration Method

Methods for characterization of the structural strength or consistency of semisolid materials which are scheduled for inclusion in the United States Pharmacopeia USP 915 and USP 1912, are useful for understanding the performance and quality stability of various pharmaceutical products. These USP chapters have shown that comparative evaluations of characteristics between semisolid materials are possible through evaluation of structural strength. As representative characteristics of pharmaceutical products related to structural strength, the ease of application and quality of spreading of ointments and lotions, resistance to dripping of liquid preparations for external use, and ease of application of adhesives for transdermal patches can be mentioned. In the past, majority of evaluations of the structural strength of pharmaceutical products were conducted by sensory evaluation. However, the need for quantitative evaluation of the structural strength of pharmaceuticals in order to ensure a stable supply of products with appropriate viscosity has become apparent in recent years, but until now, there had been no officially recognized method for quantitative evaluations of structural strength in the pharmaceutical industry. By providing measurement methods related to the characterization of pharmaceutical products in USP 915 and USP 1912, it is hoped that techniques which enable quantitative evaluation of the viscoelasticity of pharmaceutical products will gain official recognition, and a stable supply of products and more accurate comparative evaluations of products under development will be possible. Four evaluation methods for pharmaceutical products, namely, Strain ramp measurement, Shear rate ramp measurement, Oscillation amplitude sweep measurement, and Penetrometry measurement, are scheduled for inclusion in USP 915. Of these four methods, this article introduces the constant-speed measurement method as one evaluation method by penetrometry measurement. Because a predetermined conical test jig geometry is used with this method, it is not necessary to select a jig, and since the test is to measure the cone penetration by the penetration depth of the conical test jig, the test analyst can evaluate the data by a simply, easy-to understand method. In connection with penetration depth, details are provided in USP 1912, and the various characteristic values, including penetration depth, are explained from the theoretical viewpoint referring to the standard test methods ASTM D217 and ASTM D937, which were established for the semisolid substances such as industrial grease and petrolatum, respectively. This article introduces examples of application of the penetration method in tests of a medical hand cream, which is sold commercially as a medicine, and a toothpaste known for displaying test speed dependency of viscosity as the pharmaceutical products.

Document Number:
i267, LAAN-A-AG-E026
Product Type:
Material Testing, Universal / Tensile Testing
Structural Strength of Semisolids, USP 915, USP 1912, Penetration Method, Pharma & Biopharma, QA/QC Manufacturing, EZ-SX Food Texture Analyzer
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For Research Use Only. Not for use in diagnostic procedures.

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