Re: 4Comp.mod.

From: alison@c255.ucsf.EDU (ABoeckmann) Subject: Re: 4Comp.mod. Date: 28 Sep 1998 16:13:20 -0400 Ralph Quadflieg asked about a 4 compartment model. The error messages arise because LINK clauses in $MODEL are used only with a user-written PK routine *and* with either ADVAN5 or ADVAN7. With $PK, he should omit the LINK clauses. 1) With ADVAN6 8 or 9, use a $DES block to define the differential equations, using the K's defined in $PK. E.g., $DES DADT(1)=-KA*A(1) etc. 2) Since the kinetics are linear, ADVAN5 or ADVAN7 can be used. NMTRAN will understand that these statments in $PK imply the links between compartments, providing that the lower case k's are changed to upper case K's: K23 = CL23/V2 K32 = CL23/V3 K24 = CL24/V2 K42 = CL24/V4 K20 = CL20/V2 Note that the following are also needed: K12=KA and a model for V1. Here is a better approach. With NONMEM V, the analytic solution to the 4 compartment problem has been supplied as ADVAN12. This will give faster run times than the general ADVAN routines 5,6,7,8,9. Omit the $MODEL block. Use the original $PK block (with uppercase k's as noted above). With ADVAN12 TRANS1, the statement K12=KA is not needed, but K=K20 is needed. It is also possible to use ADVAN12 with TRANS4. This is a very similar parameterization, with slightly different notation. See Users Guide VIII, ADVAN12 and TRANS4 entries (or nmhelp advan12, nmhelp trans4), for the details.