Stata 15 help for pkexamine

[R] pkexamine -- Calculate pharmacokinetic measures

Syntax

pkexamine time concentration [if] [in] [, options]

options Description ------------------------------------------------------------------------- Main fit(#) use # points to estimate AUC; default is fit(3) trapezoid use trapezoidal rule; default is cubic splines graph graph the AUC line graph the linear extension log graph the log extension exp(#) plot the exponential fit for the AUC (0 to infinity)

AUC plot cline_options affect rendition of plotted points connected by lines marker_options change look of markers (color, size, etc.) marker_label_options add marker labels; change look or position

Add plots addplot(plot) add other plots to the generated graph

Y axis, X axis, Titles, Legend, Overall twoway_options any options other than by() documented in [G-3] twoway_options ------------------------------------------------------------------------- by is allowed; see [D] by.

Menu

Statistics > Epidemiology and related > Other > Pharmacokinetic measures

Description

pkexamine calculates pharmacokinetic measures from time-and-concentration subject-level data. pkexamine computes and displays the maximum measured concentration, the time at the maximum measured concentration, the time of the last measurement, the elimination time, the half-life, and the area under the concentration-time curve (AUC). Three estimates of the area under the concentration-time curve from 0 to infinity (AUC) are also calculated.

pkexamine is one of the pk commands. Please read pk before reading this entry.

Options

+------+ ----+ Main +-------------------------------------------------------------

fit(#) specifies the number of points, counting back from the last measurement, to use in fitting the extension to estimate AUC from 0 to infinity. The default is fit(3), or the last three points. This should be viewed as a minimum; the appropriate number of points will depend on your data.

trapezoid specifies that the trapezoidal rule be used to calculate the AUC. The default is cubic splines, which give better results for most functions. When the curve is irregular, trapezoid may give better results.

graph tells pkexamine to graph the concentration-time curve.

line and log specify the estimates of the AUC from 0 to infinity to display when graphing the AUC from 0 to infinity. These options are ignored, unless they are specified with the graph option.

exp(#) specifies that the exponential fit for the AUC from 0 to infinity be plotted. You must specify the maximum time value to which you want to plot the curve, and this time value must be greater than the maximum time measurement in the data. If you specify 0, the curve will be plotted to the point at which the linear extension would cross the x axis. This option is not valid with the line or log option and is ignored, unless the graph option is also specified.

+----------+ ----+ AUC plot +---------------------------------------------------------

cline_options affect the rendition of the plotted points connected by lines; see [G-3] cline_options.

marker_options specify the look of markers. This look includes the marker symbol, the marker size, and its color and outline; see [G-3] marker_options.

marker_label_options specify if and how the markers are to be labeled; see [G-3] marker_label_options.

+-----------+ ----+ Add plots +--------------------------------------------------------

addplot(plot) provides a way to add other plots to the generated graph; see [G-3] addplot_option.

+-----------------------------------------+ ----+ Y axis, X axis, Titles, Legend, Overall +--------------------------

twoway_options are any of the options documented in [G-3] twoway_options, excluding by(). These include options for titling the graph (see [G-3] title_options) and for saving the graph to disk (see [G-3] saving_option).

Examples

. webuse auc (setup) . pkexamine time conc (show measures) . pkexamine time conc, fit(7) (use last 7 point to fit model) . pkexamine time conc, trapezoid (use trapezoidal rule in calculating AUC) . pkexamine time conc, graph (graph the AUC)

Stored results

pkexamine stores the following in r():

Scalars r(auc) area under the concentration curve r(half) half-life of the drug r(ke) elimination rate r(tmax) time at last concentration measurement r(cmax) maximum concentration r(tomc) time of maximum concentration r(auc_line) AUC_{0,infinity} estimated with a linear fit r(auc_exp) AUC_{0,infinity} estimated with an exponential fit r(auc_ln) AUC_{0,infinity} estimated with a linear fit of the natural log


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