Con't: fast and slow absorption

From: Jian Xu alanub@yahoo.com Subject: [NMusers] Con't: fast and slow absorption Date: Wed, 15 Nov 2006 08:24:45 -0800 (PST) Dear NONMEM Users, I just came across the topic: fast and slow absorption in User archive. ( http://www.cognigencorp.com/nonmem/nm/99may081995.html) Joachim Grevel suggested another way to code this process: "I used ADVAN5 with 2 Depot compartments linked by first-order rate constants to the Central compartment (Compartment 3). It is assumed that DEPOT1 has availability F1 and that DEPOT2 has availability F2=1-F1. Furthermore, both Depot compartments have different lag times (ALAG1 and ALAG2) and different absorption rate constants (K13 and K23). When all these parameters are modelled simultaneously, one can have two types of absorption occur at the same time or one can restrict the difference between ALAG1 and ALAG2." I am not an experienced NONMEM user, and he did not provide code to describe this two DEPOTs approach. To me, F1 or F2 can not be simply coded as bioavailability since the central compartment will receive drug from both DEPOT1 (F1) and DEPOT2 (1-F1) (as bioavailability, normally we can just code in $ERROR as Y(1)=A(1)/V1*F)? Would someone kindly provide some hints to code this process especially when ADVAN5 or 6 used? Thanks in advance, Jian