Using DTA and DTAARRAY variables and programming in WinNonlin ASCII models to streamline user-defined calculation and...

In pharmacokinetic (PK) analysis, there are many occasions where user-defined calculations need to be performed before or after the primary PK modeling/analysis. Conventionally, these calculations are often executed outside of the primary PK analysis by pre- or post-processing data from multiple sources, manually entering formulas and multiple additional set-ups. Such analysis approaches increase the risk of generating data defects and can employ software that is not fully compliant. We propose a method of leveraging DTA and DTAARRAY variables plus simple programming techniques in an ASCII model to automate these user-defined calculations in WinNonlin and eliminate the need for manual handling of data outside of the primary analysis. We demonstrated the application of this strategy through three case study examples. In case 1 (post-processing data), DTA variables were used to calculate three user-defined parameters in the primary PK model. In case 2 (pre-processing data), a baseline correction decision tree was programmed into the PK model to account for both the endogenous baseline level as well as the presence of residual drug. In case 3, DTAARRAY variables were used to perform a looping operation to calculate the difference factor (F1) and the similarity factor (F2) in support of in vitro bioequivalence evaluations.