Dear R users,

I am using nlme to fit a pharmacokinetic model. The base model is
parameterized in terms of CL, V1, V2 and Q.

basemodel<-nlme(Conc ~TwoCompModel(CL,Q,V1,V2,Time,ID),
data = data2, fixed=list(CL+Q+V1+V2~1),
random = pdDiag(CL+V1+V2~1),
start=c(CL=log(20),Q=log(252),V1=log(24.9),V2=log(120)),
control=list(returnObject=TRUE,msVerbose=TRUE,
msMaxIter=20,pnlsMaxIter=20,pnlsTol=1),
verbose=TRUE).

Now, I want to include covariates (age and weight) in the base model. The
relationships between CL and covariate is linear and given as the following
equation.

CL=TVCL+a*wt-b*age, where TVCL is mean clearance, a and b are coefficients
of weight and age, respectively.

How do I write this in nlme to estimate TVCL, a and b?

Any input would be appreciated.

Regards

Shailly Mehrotra
Center for Translational Medicine
School of Pharmacy
University of Maryland
Baltimore, MD, USA

	[[alternative HTML version deleted]]

