Determination of the apparent failure viscosity of tablets.

Quantitative differences in the plasticity of several direct compression excipients were found to be distinguishable using normalized work of failure determinations. New parameters were developed to characterize the importance of changes in strain rate application during a diametral crushing test. Failure viscosity was found to have a similar sensitivity to normalized work of failure measurements and was also able to distinguish small changes in plastic behaviour. In cases where it is not possible to measure tablet deformation during tablet crushing, failure viscosity determinations could provide an alternative method for characterizing differences in deformation behaviour.