I have built a n-transit compartment with single distibutional pharmacokinetic absorption model using SimBiology. This model is based on the TRANSIT model descibed in the following publication: Savic, R.M., Jonker, D.M., Kerbusch, T. et al. J Pharmacokinet Pharmacodyn (2007) 34: 711. https://doi.org/10.1007/s10928-007-9066-0
I chose to start by loading a one compartment absorption model with Clearance parmaeterization (macro parameters) and then modified the absorption reaction equation as n transit compartment that is based on an analytical solution to determine the transit compartment number as a continuous variable (not an interger).
analytical solution for number of compartments:
Single distribution compartment ODE:
transform of ODE for numerical stability when n is large:
Attache is a report summarizing how I defined the model in simbiology.
I am not sure if I have used the wrong syntax but I am seeing negative cincentrations at the first simulated timepoints as shown by this simulation plot:
The simulation should be a gradual absorption phase in contrast to typical tlag absorption models that are in the simbiology PK model library.