Dear NM-users,
We developed a PK model using NONMEM for a drug using a 2-cpt model with
time-lagged first order absorption and first order elimination. The
final model includes binomial covariates correlated with clearance,
absorption rate and bioavailability. The model is validated using a VPC.
We split our data set in an index data set to develop a Bayesian
estimator and a separated validation data set to determine its
predictive performance. We are using PFIM3.2.1 in order to determine the
optimal sampling schedule using the popPK parameters as estimated for
the index data set. However, we are having some issues, for which we
need some suggestions.
- The model has a time-lagged absorption. How can we include this in our
PFIM files?
- The covariates in our final model are coded proportionally. We use an
exponential random effect model (see below). How can we include our
covariates in this model? Do we need to transform the value from the
nonmem output file?
Nonmem: CL=THETA(1)*THETA(2)**COV
PFIM:
# covariate is additive on log parameters if exponential random effect
model (Trand=2)
#-----------------------------------------------------------------------
beta.covariate<-list(COV=list(c(log(1.93))))
- We have a covariate and interpatient variability on bioavailability.
How can we code this in PFIM?
- Furthermore, we developed a second model using Erlang distribution to
describe the absorption. Does anybody know how to implement this in PFIM?
Thank you very much in advance for your help.
Kind regards,
Annick Rousseau and Brenda de Winter
