How to include a dynamic covariate

Dears We have been working in a pk model to prove that a drug can changes its own kinetics as a function of dose. Standards pharmacokinetics models assume a linear relationship between dose and plasma concentrations.Till now our results show clearly a non-linearity between dose and drug-kinetics, using dose as covariate. But we are interested to include a dynamic covariate like CO, CI and/or MABP as covariate using differential equation solutions . Any suggestions, reference papers, ideas Thanks so much Olinto Olinto-Jose Linares-Perdomo, BS in Electrical Engineering, M.S., Ph.D. Biomedical Informatics Department & Pharmaceutics Department. University of Utah-USA Office:(801)-585-5287 Cell: 001-(801)-783-9487 Fax: (801)-581-3467 ------------------------------------- Confidentiality Note: This message is intended for use only by the individual or entity to which it is addressed and may contain information that is privileged, confidential, and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient or the employee or agent responsible for delivering the message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please contact the sender immediately and erase it