Bayesian settings

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Click the Bayesian button on the Drug model editor dialog.

 

This dialog is used to edit the weighting of model and serum level assay data.  Below is an explanation of the inputs.  As with any of the model parameters, please do not edit these parameters unless you are certain of their validity.

 

Standard deviation (SD) of population parameters

After correcting for age, weight, sex, and renal function there is a coefficient of variation of population pharmacokinetic parameters that is on the order of 20-50%.  In the aminoglycoside model, 40% is used as the default value for the variability for both clearance and distribution volume.  In the vancomycin model,  the default variability for clearance is 40%, the default distribution volume variability is 20%.

 

Standard deviation (SD) of drug assay procedure

A reasonable coefficient of variation of serum assay error is on the order of 5 to 15%.  According to published data, serum assay error patterns are well represented by a second order polynomial:

SAE = SD1+ (SD2 * Cp) + (SD3 * Cp^2)

 

Weighting of serum level data                

Individual data points are then weighted according to the serum assay error (SAE), a fixed variability (SD4) which accounts for environmental errors, and the time from dose administration (Time) which gives more weight to the trough level:

Weight(i) = 1 / [ {Cp(i) * SAE + SD4} * {1.005 ^ [Interval - Time(i)] } ] ^ 2

 

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