Influences of technological and other pre-systemic modifications on the drug performance play a pivotal role in drug development and optimization. The paper evaluates these influences within a framework of the sensitivity theory. Deviations of the drug performance that were caused by modified pre-systemic parameters are predicted and compared with those obtained in vivo. A close correspondence between them demonstrates feasibility of the approach presented and its usability as an alternative or suplementary means of the in vitro-in vivo correlation analysis.