RE: advan8 vs. advan13

________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Nick Holford Sent: Sunday, November 01, 2009 1:57 PM To: nmusers Subject: Re: [NMusers] advan8 vs. advan13 Pavel, The TRANSn option is only meaningful for those ADVANs (i.e. 1-4,11,12) which implement a closed form solution of the PK model. TRANS1 does nothing except keep the linker happy. Because it is the default it need never be explicitly specified for ADVAN5-9,13. "TRANS1 Dummy, or null, translator; may be used with all ADVAN routines. It is the default." NONMEM7 Help Adding it to those ADVANs which solve ODEs or use matrix exponential solutions should make no difference to anything. If you find that adding TRANS1 changes the behaviour of ADVAN8 then this is a bug. Nick [email protected] wrote: > Hello Nonmem Users, > > When I tried simple simulations and changed advan13 to advan8, some concentrations changed. Equations were stiff. Then I added TRANS1 to the $SUBROUTINE statements. ADVAN13 output did not change. ADVAN8 output changed and looked exactly like ADVAN13 output. Do you know what happened? > > (Another thing I noted is that when IMP is used, the lower boundary for bioavailability cannot be 0.) > > Thanks, > Pavel > > ----- Original Message ----- > From: [email protected] > Date: Sunday, November 1, 2009 8:34 am > Subject: Re: [NMusers] advan8 vs. advan13 > To: [email protected] > > > It seems like advan8 has integration difficulties when both LAG > > time and variability in Ka are implemented. Method=IMP has > > dificulties when advan8 has integration difficulties. Instead > > if reporting issues, it keeps running. The objective function > > is very low even when bioavailability is almost zero. Removing > > LAG and eta of Ka may fix it. > > > > ----- Original Message ----- > > From: [email protected] > > Date: Sunday, November 1, 2009 12:04 am > > Subject: [NMusers] advan8 vs. advan13 > > To: [email protected] > > > > > Hello NONMEM users, > > > > > > Because advan13 was recomended for both stiff and nonstiff > > > differential equations, I used it for stiff differential > > > equations. It appeared that some results looked too sensitive > > > to a parameters representing a "slow" processes. I did not > > > observe it with nonmem6. When I used advan8, the objective > > > function changed from 10228.853 (the final value; diagnostic > > > plots looked good) to 5512.594 (the first value; I im still > > > waiting for the final value of the objective function). > > > > > > Does it mean that advan13 should be used with caution when the > > > equations are stiff or advan13 cannot replace advan8? > > > > > > Thanks, > > > Pavel > > > > > -- Nick Holford, Professor Clinical Pharmacology Dept Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand [email protected] tel:+64(9)923-6730 fax:+64(9)373-7090 mobile: +64 21 46 23 53 http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford