Good afternoon everyone,

I have pharmacokinetic data from a population only post-infusion plasma concentrations. S, plasma drug levels were obtained following the end of the infusion. So, the peak plasma concentrations are at time zero and decreases from there.

My question is that, how do I implement this popPK of post-infusion data in Monolix?

I plan to use “X” as the regressor with the initial conditions at time=0. Do you have any suggestions?

Here is what I get when I try the initial parameter estimates:

Here is the model that I am using:

[LONGITUDINAL]

input = {Cl, V1, Q, V2, Cc_init}

Cc_init = {use=regressor}

EQUATION:

V = V1

k = Cl/V1

k12 = Q/V1

k21 = Q/V2

Cc = pkmodel(V, k, k12, k21)

Cc_out = Cc+Cc_init

OUTPUT:

output = Cc_out

Thanks…