RE: Time varying volume of distribution implementation
Dear Thorsten,
As suggested by other, implementing a time dependent covariate in $DES should
be the way to go. A quick workaround could also be inserting dummy observations
at regular intervals in your dataset e.g. when using ADVAN5.
Just out of scientific curiosity:
Are you investigating total (maternal + fetal) body weight as a covariate for
volume of distribution? I would expect that both maternal body weight (water
retention and increase in fat tissue) and placental-fetal-weight (growth,
increase in volume of amniotic fluid) may increase during pregnancy and that
depending on the drug (whether it penetrates the placenta) this has
implications for your analysis.
Sincerely,
Rob
---
Dr. R. ter Heine, hospital pharmacist-clinical pharmacologist
Head of Clinical Trials Unit, Dept. of Pharmacy
Radboudumc
Quoted reply history
Van: [email protected] [mailto:[email protected]] Namens
Thorsten Lehr
Verzonden: vrijdag 22 april 2016 23:34
Aan: [email protected]
Onderwerp: [NMusers] Time varying volume of distribution implementation
Dear NMusers,
I'm modeling a compound where body weight has a known impact on the volume of
distribution. This compound is investigated in pregnant women over a long
period (from gestational age of 8 weeks until they give birth). Consequently,
the body weight changes over time and I have a decent formula to describe the
individual body weight change. The PK model has to be coded by ODEs. Does
anyone has experience how to integrate a time varying volume of distribution if
differential equations are used?
Best regards
Thorsten
--
Thorsten Lehr, PhD
Junior Professor of Clinical Pharmacy
Saarland University
Campus C2 2
66123 Saarbrücken
Germany
Office: +49/681/302-70255
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[email protected]<mailto:[email protected]>
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