Double Peak PK modeling

Phoenix Certara Forums Modelling and Simulation
1

I am working on a PK model for a PK profile with double peaks . I found a paper reporting the same kind of case with two gastric emptying rates. I am not sure how to restrict the time ranges those are associated with different gastric emptying time (highlighted on attached paper. Could you do me a favor to take a look at my model and see how to improve it? In my model, T1 is tend and T2 is tlag those are mentioned on attached paper respectively. It sounds like kg2 is not well defined on my model.

Thanks

Jian

Double peak PK.phxproj (1.74 MB)Modeling of double peak PK profile.pdf (486 KB)

2

Jian, here is some proposed code.

test(){
kg = t < T1? kg1:
t > T1+deltaT? kg1:
kg2

deriv(Ast = -kg * Ast)
deriv(Aint = kg * Ast - ka * Aint)
deriv(Cp = (ka Aint + k21 * Aper)/ V - (k12 + ke) * Cp)
deriv(Aper = k12 * Cp * V - k21 * Aper)
dosepoint(Ast)
error(CEps = 0.1)
observe(CObs = Cp(1 + CEps))
fixef(ka = c(, 4.5, ))
fixef(k12 = c(, 5.8, ))
fixef(k21 = c(, 0.9, ))
fixef(ke = c(, 1.7, ))
fixef(V = c(, 0.7, ))
fixef(kg1 = c(, 0.5,))
fixef(kg2 = c(, 0.1,))

T1 is Tend

fixef(T1 = c(, 3, ))

T2 is Tlag

deltaT is Tlag - Tend

fixef(deltaT = c(0, 3, ))
}

I would also suggest that you could instead call T1, Tend in the code etc. then the code is more transparent

Also in your model it is possible to append all your doses into one worksheet and dit them together, you can even run them as Naive pool population without an NLME license if you feel the individual data is too sparse to fit well. that would be better than meaning the data first I think.

[color=#000000][font=calibri][size=2] Simon.