Re: log transformed data and multi compartment PK

From: Leonid Gibiansky leonidg@metrumrg.com Subject: Re: [NMusers] log transformed data and multi compartment PK Date: Tue, 26 Jul 2005 18:17:03 -0400 1. I would use ADVAN5 or ADVAN7 rather then differential equations if you want to speed up the process 2. It is better to follow conventions and use K13 - K31 for the mass exchange between compartments 1 and 3, rather than K12 - K21 (and similarly for all the other coefficients) 3. If F (prediction) is equal to zero, NONMEM will crash. Just in case, use IPRED=F IF(IPRED.LT. some small number, say LLOQ, 0.01) IPRED= same number, say 0.01 Y1=LOG(IPRED)+ERR(1) 4. Try to start with just 2-3 random effects first, and add more if needed/supported by the data 5. You have identifiability problem. You need either to fix S1=S2 or assume complete metabolism (KE=0) or assume metabolization fraction (KA= some.fixed.number*KE) 6. What is the meaning of KL, is it reversible metabolism? Good luck Leonid