Bayesian estimation: a specific case

From: Quyen.Ho-Nguyen@serono.com Subject: Bayesian estimation: a specific case Date: Wed, 4 Oct 2000 13:58:25 +0100 Dear NONMEM users, Thank you very much to all of you who took time to respond to my message. I understand better now... However, I am wondering if the solution suggested by most of you ("use the initial estimates of all parameters to the estimates from pop1 and then run pop2 data with $EST MAXEVAL=0 POSTHOC) is fully applicable in my case. I need to better explain the circumstances of my problem. Pop1: 12 healthy subjects, 6 extravascular administrations, rich data including 10 blood samples (until 48 h post-dose) following the first administration, 10 blood samples following the last administration, and through concentrations (1 sample before each administration).The PK model is complicated (complicated input model) with 7 parameters in total to be estimated. Pop2: 12 patients, 6 extravascular administrations, sparse data including 5 blood samples following the first administration, 5 blood samples following the 4th administration and through concentrations (1 sample before each administration). The PK developed in pop1 can not describe data of the study 2 (due to a low number of samples per subject in pop2). By non compartmental approach, it "seems" that the PK between Pop1 and Pop2 are comparable (in terms of Cmax, AUC during the administration interval, Cthrough). The aim is to evaluate the total exposure (total AUC) of the patients in pop2. The question is: can I use the model of pop1to calculate the Posthoc PK (CL, V, etc...) of pop2? Is it relevant to apply the PK model found in Pop1 to the Pop2, even if data of Pop2 can not describe this model, due to a low number of samples per patient in Pop2 and to the complicated PK model ? thank you for your feed back best regards, Quyen