Semisolid quality control

The key parameter for any drug product is its efficacy as demonstrated in controlled clinical trials. The time and expense associated with such trials make them unsuitable as routine quality control methods. Therefore, in vitro surrogate tests are often used to assure that product quality and performance are maintained over time and in the presence of change. A variety of physical and chemical tests commonly performed on semisolid products and their components (e.g., solubility, particle size and crystalline form of the active component, viscosity, and homogeneity of the product) have historically provided reasonable evidence of consistent performance. More recently, in vitro release testing has shown promise as a means to comprehensively assure consistent delivery of the active component(s) from semisolid products. 

Schwarz, E. Pfeffer, S. Use of subambient DSC for liquid and semisolid dosage form pharmaceutical product development and quality control. J. Therm. Anal. 1997, 48, 557-567. 

The rheological behaviour of liquids and semisolids can be described as discussed in sections 7.3.10 and 7.4.4 of Chapter 7. Viscosity monitoring can be used as a quality control procedure, but some very practical rheological tests may be carried out. Some are discussed here. 

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