Re: Rounding Error 134

Date: Tue, 14 Aug 2001 16:56:36 +1200 From: Nick Holford <n.holford@auckland.ac.nz> Subject: Re: Rounding Error 134 Qun, The rounding error message is very common. I expect to get it most of the time when developing NONMEM models. It is especially likely when you use the final estimates from a run that minimized successfully. NONMEM needs to 'feel its way around' a bit to get sig digs. If you try starting with estimates displace by say 10% from the final values you may have more luck. I think your model is perhaps too constrained. You only have ETA on CL, V2 and ALAG1. You should try putting ETA on the other PK parameters (especially KA) and also use a BLOCK structure to capture the covariance. You have multiple doses for each subject so you might also want to try estimating between occasion variability. Finally, graphs of the fits dont show much of a 2 cpt behaviour. You might find that a one compartment model is adequate. Nick -- Nick Holford, Divn Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand email:n.holford@auckland.ac.nz tel:+64(9)373-7599x6730 fax:373-7556 http://www.phm.auckland.ac.nz/Staff/NHolford/nholford.htm