Analysis of Steady State Data

(S=Maier%S=Maier%G=Gary%I=A%O=STERLING%OU1=PRD1%KODAK@mcimail.com) - 5 Dec 94 I would like to describe a problem that I ran into when using NONMEM on our VAX computer system. We recently completed a phase III study in which plasma concentrations as well as PD measurements were collected under steady-state conditions. A nonmem data set was created assuming these conditions with SS values of 1 and an interdose interval of 24 hours. Advan4 and trans 3 were utilized base upon prior information. To my surprise, I noticed that once the estimation step was invoked, all converted parameter estimates and gradients were zero and did not change throughout the iteration procedure, despite large numerical reductions in the objective function. When this data set and associated nmtran records were transferred to a SUN workstation no problems were encountered. Has anyone out there ever experienced similar difficulties?