PK models for rich and sparse sampling

From: Gordi, Toufigh Toufigh.Gordi@cvt.com Subject: [NMusers] PK models for rich and sparse sampling Date: Fri, May 28, 2004 7:57 pm Dear all, I was recently involved in PK/PD modeling of a compound, where initial modeling on rich data indicated a two-compartment model to describe the data best. Data from a later study with much fewer samples per subject suggested a one-compartment model to be the best model to fit the data to. This is not surprising, since there simply was not enough data available during the early phase of the drug disposition to characterize the two phases of the concentration decline in the latter study the way it was possible in the former study. Interestingly, parameter estimates were quite similar in both models. I would like to hear your comments on how to proceed with the modeling of this compound. Should one fix the estimates from the rich-data model and fit the more complex model to the sparse data or should I use the simpler model in future modeling, which will include PD modeling? In other words, how can I best use the prior information when dealing with the sparsely sampled data? Any reference would be greatly appreciated. I mho, it would be a waste of data NOT to use the more complex model. Toufigh Gordi