NONMEM Users Network Archive

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Re: Variability on infusion duration

From: Leonid Gibiansky <lgibiansky>
Date: Wed, 5 Aug 2020 12:50:33 -0400

may be
D1=DUR*EXP(ETA(1))
IF(D1.GT.DocumentedInfusionDuration) D1=DocumentedInfusionDuration

On 8/5/2020 12:18 PM, Patricia Kleiner wrote:
> Dear all,
>
> I am developing a PK model for a drug administered as a long-term
> infusion of 48 hours using an elastomeric pump. End of infusion was
> documented, but sometimes the elastomeric pump was already empty at this
> time. Therefore variability of the concentration measurements observed
> at this time is quite high.
> To address this issue, I try to include variability on infusion duration
> assigning the RATE data item in my dataset to -2 and model duration in
> the PK routine. Since the "true" infusion duration can only be shorter
> than the documented one, implementing IIV with a log-normal distribution
> (D1=DUR*EXP(ETA(1)) cannot describe the situation.
>
> I tried the following expression, where DUR ist the documented infusion
> duration:
>
> D1=DUR-THETA(1)*EXP(ETA(1))
>
> It works but does not really describe the situation either, since I
> expect the deviations from my infusion duration to be left skewed. I was
> wondering if there are any other possibilities to incorporate
> variability in a more suitable way? All suggestions will be highly
> appreciated!
>
>
> Thank you very much in advance!
> Patricia
>
>
>
Received on Wed Aug 05 2020 - 12:50:33 EDT

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