Thanks Bernd for your help.
I think I need to add a function to describe enterohepatic recycling but I am not sure how to add it to PML
Here is the code "Drug is administered once" No dosing interval
test(){
# ntr is the structural parameter representing one less than the number of transit stages.
transit(Aa, mtt, ntr, max=50, out=-Aa*Ka)
deriv(A1 = Ka * Aa - Cl * C - Cl2 * (C - C2))
deriv(A2 = Cl2 * (C - C2))
dosepoint(Aa)
C = A1 / V
C2 = A2 / V2
error(CEps = 0.1)
observe(CObs = C + CEps * sqrt(1 + C^2 * (CMultStdev/sigma())^2))
stparm(Ka = tvKa * exp(nKa))
stparm(V = tvV * exp(nV))
stparm(V2 = tvV2 * exp(nV2))
stparm(Cl = tvCl * exp(nCl))
stparm(Cl2 = tvCl2 * exp(nCl2))
stparm(mtt = tvmtt * exp(nmtt))
stparm(ntr = tvntr) # fixed
stparm(CMultStdev = tvCMultStdev)
fixef(tvKa = c(, 1, ))
fixef(tvV = c(, 162929.74, ))
fixef(tvV2 = c(, 625466, ))
fixef(tvCl = c(, 7243, ))
fixef(tvCl2 = c(, 7243, ))
fixef(tvmtt = c(,1.05, ))
fixef(tvntr(freeze) =c(,7,))
fixef(tvCMultStdev = c(,1, ))
ranef(diag(nV, nCl, nKa, nV2, nCl2, nmtt) = c(1, 1, 1, 1, 1, 1))
}
Thanks !!