Hi, all friends,
I want to record the fraction of drug absorbed in each intestinal segment, so I define a set of parameters with rate rule like: AbFraction_Colon= ((PeffColon*2/organismRadiusColon+paracellularAbsorption*organismFluxMucosaSerosa/Colon)*Colon.DrugDissolved)*Colon/InitialDose The attached figure shows the simulation result that overall PK profile (purple) seems OK, but I don't know why the absorption fraction line (red) starts from value of 1. Does anyone know the cause?
By the way, I am using model modified from "generic PBPK model"
Thanks for comment.
3 Comments
Time Descending
Hi Wei, could you change the rule type from 'rate rule' to 'repeated assignment'? A rate rule is an ordinary differential equation where the right-hand side represents terms of the ODE and the left-hand side represents the dR/dt. A repeated assignment is not a differential equation but just an algebraic equation that is evaluated at every timepoint (hence the name repeated assignment). The value of the RHS is assigned to the LHS at every time point. More on the difference between different types of rules can be found here: explanation of different rules Let me know if that solves your problem.
In future, do you mind asking your questions in the 'Answers' section of the SimBiology Community website? We like to keep the 'Discussion' section for topics that don't necessarily have an answer but where multiple opinions could be valuable. Best,
Sietse
I double check my model and find I didn't chage the value of 1 of those parameters. I didn't realize that this value would influence the simulation result. When I change this value to 0, the problem is sovled.
OK，thanks for your suggestion, I will try and post question elswhere enxt time.
If I try repeated assignment instead of rate rule, I need use the integral form of the equation post above, right?
