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Hi PharmPK expert,
I have a few questions about modeling oral absorption using Phoenix.
1. if there is a first order plus zero order oral absorption, how to model it in Phoenix. I tried
below PML code (for a one compartment model):
deriv(Aa = - (Aa * Ka)-K0)
deriv(A1 = - (Cl * C) + (Aa * Ka + K0))
where Ka is the first order absorption rate constant and K0 is the zero-order absorption rate.
Is it OK? any identifiability problem? I do not have absorption compartment data.
2. I want to add bioavailability. I know if I use graphic modeling, I can check the Bioavail
Checkbox in the Aa compartment. This converts to the change of dosepoint statement in PML as below.
Here F is defined as Bioavailability.
dosepoint(Aa, bioavail = (F), idosevar = AaDose, infdosevar = AaInfDose, infratevar = AaInfRate)
But if I want to model F using logit transformation as F= exp(LGTF)/(1+exp(LGTF)), LGTF=Theta1. How
to realize it in Phoenix (define F as the Bioavailability)?
BTW, I do not know the meaning of "idosevar = AaDose, infdosevar = AaInfDose, infratevar =
AaInfRate" in the above dosepoint statement. Can anybody give an explanation? (if it is not related,
I guess I can delete them in the code.)
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