Hi Certara team,
I'm just confirming (a) whether my syntax is correct for two different baseline models where there is endogenous drug in the body and
( whether there is an easier GUI or build-in way to do this..
I use the two simple examples of a fixed, stable baseline and one where there is synthesis but no feedback:
or do these need to be coded in only as user-define models:
(1) Simple 1-comp with extravascular absorption
deriv(Aa = - Ka * Aa)
deriv(A1 = Ka * Aa - Cl * C)
C = A1 / V
error(CEps = 1)
observe(CObs = Base + C * (1 + CEps)) #where the observed value is the Cpred with error + baseline?
where base is a structural parameter that is estimated:
stparm(Base=tvBase*exp(nBase) #defined as the baseline concentration with some interindividual variability
fixef(tvBase=c(,1,))
stparm(Ka = tvKa * exp(nKa))
stparm(V = tvV * exp(nV))
stparm(Cl = tvCl * exp(nCl))
fixef(tvKa = c(, 1, ))
fixef(tvV = c(, 1, ))
fixef(tvCl = c(, 1, ))
ranef(diag(nKa, nV, nCl, nBase) = c(1, 1, 1,1)
(2) baseline which is being continuously produced at a stable rate without any feedback loop
deriv(Aa = - Ka * Aa)
deriv(A1 = (kbase_pro+ Ka )* Aa - Cl * C)
C = A1 / V
error(CEps = 1)
observe(CObs = C* (1 + CEps)) #here the assumption is the observed is a combined amount of baseline and exogenous drug
where base is a structural parameter that is estimated:
stparm(kbase_prod=tvbase_prod*exp(nbase_prod) #defining baseline production rate constant
fixef(tvBase=c(,1,))
stparm(Ka = tvKa * exp(nKa))
stparm(V = tvV * exp(nV))
stparm(Cl = tvCl * exp(nCl))
fixef(tvKa = c(, 1, ))
fixef(tvV = c(, 1, ))
fixef(tvCl = c(, 1, ))
ranef(diag(nKa, nV, nCl, nkbase_prod) = c(1, 1, 1,1)
Thank you,
Elliot