Pharmacokinetic calculations using EquivTest

All Pharmacokinetic Calculations in EquivTest are based on non-compartmental methods of analysis for the estimation of Pharmacokinetic Parameters.

This page is an example of how EquivTest calculates pharmacokinetic measurements.

The data contains blood concentration values measured at 24 sampling points, for 18 subjects in a 2 x 2 crossover study. There are two treatment groups – Reference and Test, and two periods – 1 and 2.

The data is stored in the format of multiple variables per subject, i.e. the concentration values for every subject are stored in separate columns. EquivTest also handles data in the format of multiple records per subject, i.e. concentration values for every subject are stored in one column with a separate variable to identify the sampling point. You can change between these two formats at any stage by clicking on the Settings menu and selecting Advanced Settings, and from the Select Spreadsheet type section, select either“Multi Variables/Subject” or “Multi Records/Subject”.

You can immediately look at some summary statistics for this data by clicking on the Results tab. This will give the Minimum, Maximum, Mean, Median etc., concentration value at each of the sampling points for each of the treatment groups.

To obtain the actual pharmacokinetic results, you must first look at the concentration/time curves for each subject and select the point from which you want to calculate the terminal elimination rate. To view all the concentration/time curves, click on the Subject column heading to select all the rows in the datasheet, and then click on the Calc PK Params button.

This opens a new screen which contains two plots for each treatment for every subject. The plot on the left is a standard plot of the observed concentration values versus time, and the plot on the right is a semi-log plot (where the concentration values have been plotted on a logscale axis).You can click on any of the points on the curve to set it as the point from which the terminal elimination rate will be calculated. Once you have made your selection here, EquivTest will fill out the area directly below the plots with the resulting AUC values, and with the details of the regression line that was used to determine the terminal elimination rate, λ. You can change your selection here by simply clicking on another point on the curve and the results section will be updated appropriately so the effect of including or excluding extra data points can be evaluated immediately.

Scroll through the entire list of concentration/time curves for each subject and select a point on each of the plots for calculation of the elimination rate.

When you have completed this for each subject, you can click on the Report button to send all plots and results to an RTF file (Rich Text File) for printing or saving. Alternatively you can print all the plots and results directly from within EquivTest.

When you are satisfied with your selections, click the OK button to view the actual PK results. This will bring you back to the datasheet view and if you click on the PK Parameters tab you will see that all the various Pharmacokinetic parameters have been calculated and filled into a separate spreadsheet.

If you click on the FINISH button at the bottom of the PK Parameters tab, the program will convert the PK parameters datasheet into an EquivTest datasheet (*.etd) and you can proceed to perform equivalence testing in the main EquivTest program.

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